A281877 Numbers that are a primitive sum of two squares in more than 2 ways.

1105, 1885, 2210, 2405, 2465, 2665, 3145, 3445, 3485, 3770, 3965, 4505, 4745, 4810, 4930, 5185, 5330, 5365, 5525, 5785, 5945, 6205, 6290, 6305, 6409, 6565, 6890, 6970, 7085, 7345, 7565, 7585, 7685, 7930, 8177, 8245, 8585, 8845, 8905, 9010, 9061, 9265, 9425, 9490, 9605, 9685, 9805

Offset: 1

Author

R. J. Mathar, Feb 01 2017

Keywords

• nonn

Comments

"Primitive" means that x and y are coprime in the representations x^2+y^2.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A224450 (exactly 1 way), A224770 (exactly 2 ways), A008784, A097102.

Programs

Maple

N:= 10^4: # to get all terms <= N
V:= Vector(N):
for a from 1 to floor(sqrt(N)) do
  for b from 1 to min(a, floor(sqrt(N-a^2))) do
    if igcd(a,b) > 1 then next fi;
    r:= a^2 + b^2;
    V[r]:= V[r]+1;
od od:
select(n -> V[n] > 2, [$1..N]); # Robert Israel, Feb 07 2017