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 A371972 #10 Jul 30 2025 09:24:28
%S A371972 1,2,4,6,9,12,16,20,25,30,36,42,49,56,64,72,81,90,100,110,120,131,144,
%T A371972 156,168,182,196,210,225,239,256,270,288,306,321,342,361,380,399,420,
%U A371972 441,460,484,505,527,552,576,599,623,649,673,702,729,752,781,808,840,870,900
%N A371972 a(n) is the number of distinct areas of triangles with integer sides whose largest side is n.
%F A371972 a(n) <= A002620(n+1), with equality for n <= 20.
%F A371972 a(n) = |{A316853(k) : A316843(k) = n}| = |{A316853(k) : A173196(n) < k <= A173196(n+1)}|. - _Peter Munn_, Jul 30 2025
%o A371972 (PARI) A2(a,b,c) = {my(s=(a+b+c)/2);s*(s-a)*(s-b)*(s-c)};
%o A371972 a371972(n) = {my (A=List()); for(s2=1,n, for(s3=1,s2, if(s2+s3>n, listput(A, A2(n,s2,s3))))); #Set(A)};
%Y A371972 Cf. A316841, A371973, A371345.
%Y A371972 See the formula section for the relationships with A002620, A173196, A316843, A316853.
%K A371972 nonn
%O A371972 1,2
%A A371972 _Hugo Pfoertner_, Apr 16 2024