cp's OEIS Frontend

A376756 Number of pairs 0 <= x <= y <= n-1 such that x^2 + x*y + y^2 == 0 (mod n).

%I A376756 #21 Oct 07 2024 03:20:13
%S A376756 1,1,3,3,1,3,7,3,6,1,1,9,13,7,3,10,1,6,19,3,21,1,1,9,15,13,18,27,1,3,
%T A376756 31,10,3,1,7,21,37,19,39,3,1,21,43,3,6,1,1,30,70,15,3,51,1,18,1,27,57,
%U A376756 1,1,9,61,31,60,36,13,3,67,3,3,7,1,21,73,37,45,75,7,39,79,10,45,1,1,81,1,43,3,3,1,6,163,3,93,1,19,30,97
%N A376756 Number of pairs 0 <= x <= y <= n-1 such that x^2 + x*y + y^2 == 0 (mod n).
%H A376756 Seiichi Manyama, <a href="/A376756/b376756.txt">Table of n, a(n) for n = 1..10000</a>
%o A376756 (Python)
%o A376756 def A376756(n):
%o A376756     c = 0
%o A376756     for x in range(n):
%o A376756         z = x**2%n
%o A376756         for y in range(x,n):
%o A376756             if not (z+y*(x+y))%n:
%o A376756                 c += 1
%o A376756     return c # _Chai Wah Wu_, Oct 06 2024
%Y A376756 Cf. A000086, A046530, A087786, A290731, A376202, A376203, A376755, A376757.
%K A376756 nonn
%O A376756 1,3
%A A376756 _Tom Duff_ and _N. J. A. Sloane_, Oct 06 2024