Solutions to the N x N knights cover problem

Solutions are presented for the problem of knights covering an N x N chessboard such that every square is dominated or filled by a knight. Sixteen graphs show solutions for N ranging from three to 20. A simulated annealing computer heuristic was used to find the minimum number of knights for each value of N. Some differences from previous solutions were found including a new solution for N equals 15 and a lesser solution for N equals 14.