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 A239581 #34 Feb 16 2025 08:33:21 %S A239581 1,18,179,1788,17861,178600,1786011,17860355,178603639,1786036410, %T A239581 17860362941 %N A239581 Number of primitive Pythagorean triangles (x, y, z) with legs x < y < 10^n. %C A239581 A Pythagorean triangle is a right triangle with integer side lengths x, y, z forming a Pythagorean triple (x, y, z). It is called primitive, if gcd(x, y, z) = 1. %C A239581 Because (x, y, z) is equivalent to (y, x, z), the total number of primitive Pythagorean triangles with legs x, y < 10^n is b(n) = 2*a(n) = 2, 36, 358, 3576, 35722, ... %H A239581 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PythagoreanTriangle.html">Pythagorean Triangle</a>. %H A239581 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PythagoreanTriple.html">Pythagorean Triple</a>. %e A239581 a(1) = 1, because the only primitive Pythagorean triangle with x < y < 10 is [3, 4, 5]. %Y A239581 Cf. A008846, A020882, A020883, A020884, A046086, A046087, A101931, A101929, A239744, A239786. %K A239581 nonn,more %O A239581 1,2 %A A239581 _Martin Renner_, Mar 26 2014 %E A239581 a(6)-a(11) from _Giovanni Resta_, Mar 27 2014