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 A070147 #17 Aug 03 2025 14:07:26 %S A070147 52,252,368,372,561,659,839,957,1156,1186,1204,1582,1912,1920,1971, %T A070147 2115,2713,2774,2790,3251,3473,3728,3746,4286,4307,4313,4330,5008, %U A070147 5272,5374,6369,6389,6432,6776,6881,7223,7310,7341 %N A070147 Numbers k such that [A070080(k), A070081(k), A070082(k)] is an obtuse integer triangle with integer area. %H A070147 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeronianTriangle.html">Heronian Triangle</a>. %H A070147 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ObtuseTriangle.html">Obtuse Triangle</a>. %H A070147 Reinhard Zumkeller, <a href="/A070080/a070080.txt">Integer-sided triangles</a> %e A070147 a(1)=52: [A070080(52), A070081(52), A070082(52)] = [5,5,8]: A070085(52)=5^2+5^2-8^2=-14<0 and area^2 = s*(s-5)*(s-5)*(s-6) with s=A070083(52)/2=(5+5+8)/2=9, area^2=9*4*4*1=16*9 is an integer square, therefore A070086(52)=area=4*3=12. %Y A070147 Cf. A070142, A070136, A070146, A070141. %K A070147 nonn %O A070147 1,1 %A A070147 _Reinhard Zumkeller_, May 05 2002