A264498 Numbers n that are the product of three distinct odd primes and x^2 + y^2 = n has integer solutions.

1105, 1885, 2405, 2465, 2665, 3145, 3445, 3485, 3965, 4505, 4745, 5185, 5365, 5785, 5945, 6205, 6305, 6409, 6565, 7085, 7345, 7565, 7585, 7685, 8177, 8245, 8585, 8845, 8905, 9061, 9265, 9605, 9685, 9805, 10205, 10585, 10865, 11245, 11285, 11645, 11713, 11765

Offset: 1

Author

Colin Barker, Nov 15 2015

Keywords

• nonn

Comments

The three primes are of the form 4*k + 1.

Examples

			1105 is in the sequence because x^2 + y^2 = 1105 = 5*13*17 has solutions (x,y) = (4,33), (9,32), (12,31) and (23,24).
		

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000 (first 1000 terms from Colin Barker)

Crossrefs

Cf. A131574, A264499.

Programs

PARI

dop(d, nmax) = {
  my(L=List(), v=vector(d,m,1)~, f);
  for(n=1, nmax,
    f=factorint(n);
    if(#f~==d && f[1,1]>2 && f[,2]==v && f[,1]%4==v, listput(L, n))
  );
  Vec(L)
}
dop(3, 15000)