A281877 - OEIS

%I #7 Feb 07 2017 10:46:59

%S 1105,1885,2210,2405,2465,2665,3145,3445,3485,3770,3965,4505,4745,

%T 4810,4930,5185,5330,5365,5525,5785,5945,6205,6290,6305,6409,6565,

%U 6890,6970,7085,7345,7565,7585,7685,7930,8177,8245,8585,8845,8905,9010,9061,9265,9425,9490,9605,9685,9805

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

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

%H Robert Israel, <a href="/A281877/b281877.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 10^4: # to get all terms <= N

%p V:= Vector(N):

%p for a from 1 to floor(sqrt(N)) do

%p   for b from 1 to min(a, floor(sqrt(N-a^2))) do

%p     if igcd(a,b) > 1 then next fi;

%p     r:= a^2 + b^2;

%p     V[r]:= V[r]+1;

%p od od:

%p select(n -> V[n] > 2, [$1..N]); # _Robert Israel_, Feb 07 2017

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

%K nonn

%O 1,1

%A _R. J. Mathar_, Feb 01 2017