void Main() { // To continue, please consult the code grid in the manual. Enter the code at row 2947, column 3029. var x = FindSequenceNumber(2947, 3029); var startCode = 20151125; var code = (long)startCode; for(int i = 1; i < x; i++){ code = GetNext(code); } code.Dump(); } long GetNext(long code) => (code*252533) % 33554393; long FindSequenceNumber(int row, int col) { var rowstart = 1; for (int r = 0; r < row; r++) { rowstart += r; } var cell = rowstart; for (int c = 1; c < col; c++) { cell += row + c; } return cell; }