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 A190309 #15 Feb 16 2025 08:33:14 %S A190309 0,0,2,5,11,19,29,40,58,74,94,113,141,168,201,227,267,304,348,390,438, %T A190309 483,537,590,657,709,776,837,913,979,1057,1130,1225,1299,1396,1472, %U A190309 1576,1663,1768,1863,1974 %N A190309 Number of acute isosceles triangles, distinct up to congruence, on an n X n grid (or geoboard). %H A190309 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Geoboard.html">Geoboard</a>. %H A190309 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AcuteTriangle.html">Acute Triangle</a>. %H A190309 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IsoscelesTriangle.html">Isosceles Triangle</a>. %F A190309 a(n) = A189978(n) - A190310(n) - A108279(n). %Y A190309 Cf. A028419, A108279, A189978, A190021, A190310. %K A190309 nonn %O A190309 1,3 %A A190309 _Martin Renner_, May 08 2011