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 A309425 #8 Aug 02 2019 23:05:05
%S A309425 1,1,3,1,3,1,5,1,5,3,1,7,5,3,1,7,5,1,9,7,3,1,9,7,5,3,1,11,7,5,1,11,9,
%T A309425 7,5,3,1,13,11,9,5,3,1,13,11,7,1,15,13,11,9,7,5,3,1,15,13,11,9,7,5,3,
%U A309425 1,17,13,11,7,5,1,17,15,13,11,9,7,5,3,1,19,17,13,11,9,7,3,1
%N A309425 Difference x-y of generator pairs (x,y) {x and y coprime and not both odd, x > y} of primitive Pythagorean triangles, sorted by x and y (for same x).
%C A309425 This sequence is based on x and y (for same x) in increasing order, directly mapping to A094192 and A094193, while A126637 is sorted by the sum x+y.
%C A309425 Given any two of the four sequences below, primitive Pythagorean triangles can be generated.
%C A309425 A094192: the bigger one in generator pairs;
%C A309425 A094193: the smaller one in generator pairs;
%C A309425 A309424: the sum of generator pairs;
%C A309425 A309425: the difference of generator pairs.
%F A309425 a(n) = A094192(n) - A094193(n).
%Y A309425 Cf. A094192, A094193, A126637, A309424.
%K A309425 nonn
%O A309425 1,3
%A A309425 _Rui Lin_, Jul 31 2019