A239318 Number of visible unit cubes, aligned with a three-dimensional Cartesian mesh, completely within the first octant of a sphere centered at the origin, ordered by increasing radius.
1, 3, 6, 6, 7, 10, 12, 12, 15, 15, 18, 18, 21, 22, 25, 25, 28, 30, 30, 33, 33, 36, 39, 39, 39, 42, 42, 43, 43, 46, 49, 49, 52, 52, 54, 57, 57, 60, 63, 66, 66, 66, 66, 69, 69, 72, 72, 73, 76, 79, 79, 82, 82, 82, 82, 87, 90, 93, 93, 93, 93, 96, 96, 99, 99, 102
Offset: 1
Keywords
Crossrefs
Cf. A237707.
Programs
-
C
void printVisibleCubes(int nr) { int prev_c = 0; for (int r = 3; nr > 0; r++) { int c = 0; int c2 = 0; for (int i = 1; i*i + 2 <= r; i++) for (int j = 1; i*i + j*j + 1 <= r; j++) for (int k = 1; i*i + j*j + k*k <= r; k++) { c++; if ( (i+1)*(i+1) + j*j + k*k > r || i*i + (j+1)*(j+1) + k*k > r || i*i + j*j + (k+1)*(k+1) > r) c2++; } if (c > prev_c) { // c contains next element of A237707 printf("%d, ", c2); prev_c = c; nr--; } } }
Comments