cp's OEIS Frontend

C

#include 
#include 
typedef unsigned long long U64;
U64 isTriangular(U64 a) {  // ! Must be a < (1<<63)
    U64 s = sqrt(a*2);
    if (a>=(1ULL<<63)) exit(1);
    return (s*(s+1) == a*2);
}
int compare64(const void *p1, const void *p2) {
  if (*(U64*)p1 == *(U64*)p2) return 0;
  return (*(U64*)p1 < *(U64*)p2) ? -1 : 1;
}
#define TOP (1ULL<<19)
U64 d[TOP];
int main() {
  U64 n, x, tx, y, ty, z, tz, w, tw, p = 0;
  for (x = tx = 3; tx <= TOP; tx+=x, ++x) {
  for (y = ty = 3; ty < tx;   ty+=y, ++y) {
  for (z = tz = 3; tz < ty;   tz+=z, ++z) {
  for (w = tw = 3; tw < tz;   tw+=w, ++w) {
    n = tx*ty*tz;
    if (n x)  x = d[n], printf("%llu, ", x);
  return 0;
}