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 A249750 #11 Feb 16 2025 08:33:24
%S A249750 0,7,70,703,7026,70229,702309,7023027,70230484,702304875,7023049293,
%T A249750 70230492763,702304928492,7023049277919,70230492773355,
%U A249750 702304927727064,7023049277265686,70230492772676557
%N A249750 Number of primitive Pythagorean triples with perimeter < 10^n.
%C A249750 The ratio a(n)/10^n as n->inf is log(2)/Pi^2 = 0.70230... (Lehmer - A118858).
%H A249750 D. N. Lehmer, <a href="http://www.jstor.org/stable/2369728">Asymptotic evaluation of certain totient sums</a>, Amer. J. Math. 22, 293-335, 1900.
%H A249750 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimitivePythagoreanTriple.html">Primitive Pythagorean Triple</a>
%e A249750 a(2)=7 because there are 7 primitive solutions (a,b,c) with a+b+c<10^2.
%e A249750 (3,4,5),(5,12,13),(8,15,17),(7,24,25),(20,21,29),(12,35,37),(9,40,41)
%t A249750 lst1 = {}; Do[If[GCD[m, n]==1&&m<n&&OddQ[m+n], AppendTo[lst1, 2n(n+m)]], {n, 5000}, {m, n}]; Table[Length@Select[lst1, #<10^n &], {n, 10}]
%Y A249750 Cf. A118858.
%K A249750 nonn,more
%O A249750 1,2
%A A249750 _Frank M Jackson_, Nov 04 2014
%E A249750 a(8)-a(18) from _Hiroaki Yamanouchi_, Nov 17 2014