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 A106503 #5 Mar 31 2012 10:26:04 %S A106503 5,9,15,16,25,28,25,36,39,49,45,49,64,51,66,81,72,64,81,84,100,91,104, %T A106503 121,88,100,121,115,144,120,121,169,121,144,169,135,196,153,170,169, %U A106503 168,145,225,169,198,196,225,190,169,256,209,217,192,220,196,289,225,231 %N A106503 Middle side of primitive integer-sided triangle having an angle twice another, sorted on perimeter (A106499). %C A106503 Triple is (A106502, A106503, A106504). %Y A106503 Cf. A106499-A106506, A106410, A106420, A106430. %K A106503 nonn %O A106503 1,1 %A A106503 _Lekraj Beedassy_, May 04 2005 %E A106503 Corrected and extended by _Ray Chandler_, May 09 2005