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 A020891 #13 Jan 24 2025 11:56:03
%S A020891 4,6,8,10,10,12,14,14,16,18,18,20,22,22,24,26,26,28,28,30,30,32,34,34,
%T A020891 36,36,38,38,40,42,42,42,44,44,46,46,48,48,50,50,52,52,54,54,56,58,58,
%U A020891 60,60,60,62,62,64,66,66,66,66,68,68,70,70,72,74,74,76,76,78,78,78,78,80,82,82
%N A020891 Ordered set of c + a - b as (a,b,c) runs through all primitive Pythagorean triples with a<b<c.
%H A020891 Ray Chandler, <a href="/A020891/b020891.txt">Table of n, a(n) for n = 1..10000</a>
%F A020891 a(n) = 2*A020892(n).
%t A020891 pyth[nn_]:=Module[{tr={}}, Do[If[CoprimeQ[m,n]&&Mod[m+n,2]==1,AppendTo[tr,{m^2-n^2,2 m n,m^2+n^2}] ], {m,2,nn},{n,1,m-1}];tr]; Take[#[[3]]+#[[1]]-#[[2]]&/@(Sort/@pyth[50])//Sort,80] (* _Harvey P. Dale_, Jan 24 2025 *)
%Y A020891 Cf. A020892.
%K A020891 nonn
%O A020891 1,1
%A A020891 _Clark Kimberling_
%E A020891 Extended and corrected by _David W. Wilson_
%E A020891 Offset corrected to 1 by _Ray Chandler_, Jan 23 2020