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E. Sampathkumar has generalized a graph to a semigraph by allowing an edge to have more than two vertices. Like in the case of graphs, a complete semigraph is a semigraph in which every two vertices are adjacent to each other. In this article, we have generalized a problem noted by Gauss in 1796 about triangular numbers and shown that it is the deciding factor of when a semigraph is complete. Let P be a set with p elements and { E 1 , E 2 , … , E q } be a collection of subsets of P with ⋃ i = 1 q E i = P . We derive an expression for the maximum value of the difference ∑ j = 1 k | E i j | - ⋃ i = 1 k E i j for 2 ⩽ k ⩽ q , where every two of the sets in the collection can have at most one element in common. We show that this result helps in answering the question of whether there exists a semigraph on the vertex set P having edges { e 1 , e 2 , … , e q } , where the set E i is the set of vertices on the edge e i , 1 ⩽ i ⩽ q . Combining the above two results, we characterize a complete semigraph.

For a subset S of nonnegative integers and a vector $\mathbf {a}=(a_1,\ldots ,a_k)$ of positive integers, define the set $V^{\prime }_S(\mathbf {a})=\{ a_1s_1+\cdots +a_ks_k : s_i\in S\}-\{0\}$ . For a positive integer n, let $\mathcal T(n)$ be the set of integers greater than or equal to n. We consider the problem of finding all vectors $\mathbf {a}$ satisfying $V^{\prime }_S(\mathbf {a})=\mathcal T(n)$ when S is the set of (generalised) m-gonal numbers and n is a positive integer. In particular, we completely resolve the case when S is the set of triangular numbers.

The Barvinok-Pataki bound provides an upper bound on the rank of extreme points of a spectrahedron. This bound depends solely on the number of affine constraints of the problem, i.e., on the algebra of the problem. Specifically, the triangular number of the rank r is upper bounded by the number of affine constraints. We revisit this bound and provide a strengthened upper bound on the rank using the singularity degree of the spectrahedron. Thus we bring in the geometry and stability of the spectrahedron, i.e., increased instability as seen by higher singularity degree, yields a lower, strengthened rank bound.

We search for triangular numbers that are multiples of other triangular numbers. For any positive non-square integer multiplier, there is an infinity of multiples of triangular numbers that are triangular numbers and recurrent relations are deduced theoretically in function of two parameters. If the multiplier is a squared integer, there is either one or no solution, depending on the multiplier value.

Summary–A fair die with sides numbered from one to N is rolled. You can either receive the value shown or else pay one and roll again. If you do not like the second roll, you can pay another one an...

Some convolution-type identities involving polygonal numbers and Horadam numbers are derived. The method of proof is to properly relate the generating functions to each other. Additionally, we prove a general non-convolutional result involving these number families and discuss some of the consequences.

Finding all integers which can be written as a sum of three nonzero squares of integers has been studied by a number of authors. This question is solved under the assumption of the Generalized Riemann Hypothesis (GRH), but still remains unsolved unconditionally. In this paper, we show that out of all integers that are sums of three squares, all but finitely many can be written as [Formula: see text] for some integers [Formula: see text]. Furthermore, we explicitly describe this finite set under the GRH. From this result, we also describe further generalizations for sums of nonzero polygonal numbers. Precisely, we find all integers, under the GRH only when [Formula: see text], which are sums of [Formula: see text] nonzero triangular (generalized pentagonal and generalized octagonal, respectively) numbers for any integer [Formula: see text].

In this paper, we construct extensions of the differential field obtained from Halphen’s system of ordinary differential equations (ODEs) using quasi-modular forms of levels two, four, and six. In addition, we derive analogs of Jacobi’s derivative formula and Jacobi’s quartic identity using theta functions with rational characteristics. Moreover, we also treat representability as sums of squares, sums of triangular numbers and mixed sums of squares and triangular numbers.

The focus of this paper is on formal power series analogs of the golden ratio. We are interested in both their continued fractions expansions as well as their Laurent series expansions. Our approach studies the Hankel matrices that are determined using the coefficients of the Laurent series expansions., 26 pages, 4 figures

Triangular numbers have been of interest and continuously studied due to their beautiful representations, nice properties, and various links with other figurate numbers. For positive integers n and l, the nth l-isosceles triangular number is a generalization of triangular numbers defined to be the arithmetic sum of the formT(n, l) = 1 + (1 + l) + (1 + 2l) + · · · + (1 + (n − 1)l).In this paper, we focus on characterizations and identities for isosceles triangular numbers as well as their links with other figurate numbers. Recursive formulas for constructions of isosceles triangular numbers are given together with necessary and sufficient conditions for a positive integer to be a sum of isosceles triangular numbers. Various identities for isosceles triangular numbers are established. Results on triangular numbers can be viewed as a special case.

The triangular number Tm counts the number of dots in a triangular array formed above m dots. The first five triangular numbers are pictured in Figure 1.Fig. 1 Triangular arrays demonstrating T1,T2...

Practical nonlinear programming problem often encounters uncertainty and indecision due to various factors that cannot be controlled. To overcome these limitations, fully fuzzy rough approaches are applied to such a problem. In this paper, an effective two approaches are proposed to solve fully fuzzy rough multi-objective nonlinear programming problems (FFRMONLP) where all the variables and parameters are fuzzy rough triangular numbers. The first, based on a slice sum technique, a fully fuzzy rough multi-objective nonlinear problem has turned into five equivalent multi-objective nonlinear programming (FFMONLP) problems. The second proposed method for solving FFRMONLP problems is α-cut approach, where the triangular fuzzy rough variables and parameters of the FFRMONLP problem are converted into rough interval variables and parameters by α-level cut, moreover the rough MONLP problem turns into four MONLP problems. Furthermore, the weighted sum method is used in both proposed approaches to convert multi-objective nonlinear problems into an equivalent nonlinear programming problem. Finally, the effectiveness of the proposed procedure is demonstrated by numerical examples.

Graphs have applications in all areas of science and therefore the interest in Graph Theory is increasing everyday. They have applications in Chemistry, Pharmacology, Anthropology, Biology, Network Sciences etc. In this paper, Graph theory is connected with algebra by means of a new graph invariant Ω and define triangular graphs as graphs with a degree sequence consisting of n successive triangular numbers and use Ω and its properties to give a characterization of them. We give the conditions for the realizability of a set D of n consecutive triangular numbers and also give all possible graphs for 1≤t≤4 .

In this study, fuzzy mean and range control charts were used to follow the feeding material and concentrate production line of Eti Aluminum Co. Fuzzy control charts were collected from the factory over a period of time and compared to Shewhart control charts used by the factory. The results showed that fuzzy control charts detected errors in the production process more accurately than Shewhart control charts. This method has increased quality and efficiency. Process capability indices (PCIs) provide numerical measures as to whether a process has confirmed the defined capability prerequisite. These were used to measure the process's ability to decide how well it meets specification limits (SLs). PCIs have been implemented by companies to evaluate quality and efficiency performance. Fuzzy process capability analysis using X-R control charts gave more accurate results.