1,3

Similar to A038373 but with octant grid instead of quadrant. An octant grid is either half of a quadrant grid when divided on the diagonal and including the diagonal grid squares. It's shape is that of a right triangle with a stair step edge on the hypotenuse. Coordinates of squares satisfy x>=0 and y>=0 and x>=y.

// C++ code #define GRIDSIZE 20 void Recur(int level, int maxlevel, int rgBd[][GRIDSIZE], int i, int j, int rgCt[]) { if (i < 0 || j < 0 || i >= GRIDSIZE || j >= GRIDSIZE || level >= maxlevel || j > i || rgBd[i][j] != 0) return; rgCt[level] += 1; rgBd[i][j] = 1; Recur(level + 1, maxlevel, rgBd, i + 1, j, rgCt); Recur(level + 1, maxlevel, rgBd, i - 1, j, rgCt); Recur(level + 1, maxlevel, rgBd, i, j + 1, rgCt); Recur(level + 1, maxlevel, rgBd, i, j - 1, rgCt); rgBd[i][j] = 0; } int main(int argc, char **argv) { int rgBd[GRIDSIZE][GRIDSIZE] = {0}; int rgCt[GRIDSIZE] = {0}; int maxlevel = GRIDSIZE; if (argc > 1) { maxlevel = atoi(argv[1]); if (maxlevel < 0 || maxlevel > GRIDSIZE) { printf("Bad argument"); return 0; } } Recur(0, maxlevel, rgBd, 0, 0, rgCt); for (int i = 0; i < maxlevel; i++) printf("%2d ", rgCt[i]); return 0; }

Cf. A038373.

Sequence in context: A077055 A022951 A128305 this_sequence A049344 A080877 A007165

Adjacent sequences: A129697 A129698 A129699 this_sequence A129701 A129702 A129703

nonn

Bill Blewett (BillBle(AT)microsoft.com), Jun 01 2007