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 A020889 #11 Jan 23 2020 14:28:20 %S A020889 6,20,24,30,42,60,70,72,80,88,104,110,112,126,130,140,154,156,170,180, %T A020889 198,204,210,228,234,238,252,264,266,272,286,304,308,322,330,336,342, %U A020889 352,364,368,374,390,396,400,414,416,420,432,442,450,460,468,480,494,506,510 %N A020889 Ordered set of b + c - a as (a,b,c) runs through all primitive Pythagorean triples with a<b<c. %H A020889 Ray Chandler, <a href="/A020889/b020889.txt">Table of n, a(n) for n = 1..10000</a> %F A020889 a(n) = 2*A020890(n). %Y A020889 Cf. A020890. %K A020889 nonn %O A020889 1,1 %A A020889 _Clark Kimberling_ %E A020889 Extended and corrected by _David W. Wilson_ %E A020889 Offset corrected to 1 by _Ray Chandler_, Jan 23 2020