This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A228380 #17 Sep 29 2015 17:41:40
%S A228380 1,6,13,16,18,22,23,32,33,35,36,37,41,42,43,44,45,46,50,51,53,57,58,
%T A228380 59,60,61,63,67,69,70,74,75,77,78,79,80,83,84,85,86,88,89,90,93,94,95,
%U A228380 96,97,98,102,104,110,112,116,117,118,119,122,123,124,126,128,132,133,134,137,138,141,142,143,152
%N A228380 Positive integers N such that N = (p^2+q^2)*(r^2-s^2)/((p^2-q^2)*(r^2+s^2)) for some positive integers p,q,r,s.
%C A228380 Integer N>1 belongs to this sequence if and only if the elliptic curve y^2 = x^3 - (N^2+1)*x^2 + N^2*x has positive rank.
%o A228380 (PARI) { isA228380(n) = ellanalyticrank(ellinit([0,-(n^2+1),0,n^2,0]))[1]; } /* _Max Alekseyev_, Sep 29 2015 */
%Y A228380 Cf. A117319
%K A228380 nonn
%O A228380 1,2
%A A228380 _Thomas Bokk_, Aug 21 2013
%E A228380 More terms from _Max Alekseyev_, Sep 29 2015