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 A225207 #23 Mar 01 2023 01:49:08 %S A225207 4,347,34163,3412143,341175325,34117055318,3411700692939, %T A225207 341170025540426,34117002022924247 %N A225207 Number of primitive Pythagorean quadruples (a, b, c, d) with d < 10^n. %C A225207 a(n) ~ (1+G)*A225206(n)/Pi, where G is Catalan's constant (A006752). %H A225207 Wikipedia, <a href="http://en.wikipedia.org/wiki/Pythagorean_quadruple">Pythagorean quadruple</a> %e A225207 a(1) = 4 because there are four primitive solutions (a, b, c, d) as follows: (1, 2, 2, 3), (2, 3, 6, 7), (1, 4, 8, 9), (4, 4, 7, 9) with d < 10. %Y A225207 Cf. A096907-A096910, A225206. %K A225207 more,nonn %O A225207 1,1 %A A225207 _Arkadiusz Wesolowski_, May 01 2013 %E A225207 a(4) from _Giovanni Resta_, May 01 2013 %E A225207 a(5)-a(9) from _Max Alekseyev_, Feb 28 2023