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 A097281 #7 Dec 22 2017 18:53:15 %S A097281 0,1,2,5,9,18,35,71,144,294,601,1231,2526,5191,10672,21950,45159, %T A097281 92920,191214,393512,809864,1666775,3430425,7060297,14531166,29907455, %U A097281 61554442,126689294,260747884,536663296,1104544280,2273340315 %N A097281 Integer part of the area of integer triangle [A001611(n), A001611(n+1), A001611(n+2)]. %F A097281 a(n) = floor(sqrt(s(n) * (s(n)-A001611(n)) * (s(n)-A001611(n+1)) * (s(n)-A001611(n+2)))), where s(n) is the semiperimeter: s(n) = A097280(n)/2. %K A097281 nonn %O A097281 0,3 %A A097281 _Reinhard Zumkeller_, Aug 04 2004