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 A190310 #15 Feb 16 2025 08:33:14 %S A190310 0,0,0,1,3,5,9,12,19,24,32,37,51,57,69,80,99,107,127,136,161,176,196, %T A190310 207,246,262,286,306,343,357,399,414,460,485,517,544,605,623,659,689, %U A190310 757 %N A190310 Number of obtuse isosceles triangles, distinct up to congruence, on an n X n grid (or geoboard). %H A190310 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Geoboard.html">Geoboard</a>. %H A190310 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ObtuseTriangle.html">Obtuse Triangle</a>. %H A190310 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IsoscelesTriangle.html">Isosceles Triangle</a>. %F A190310 a(n) = A189978(n) - A190309(n) - A108279(n). %Y A190310 Cf. A028419, A108279, A189978, A190022, A190309. %K A190310 nonn %O A190310 1,5 %A A190310 _Martin Renner_, May 08 2011