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 A120252 #11 Feb 16 2025 08:33:01
%S A120252 1,4,12,13,14,28,23,27,38,33,25,81,30,52,83,44,32,101,33,80,149,73,41,
%T A120252 146,50,61,89,132,35,204,45,80,173,79,135,220,37,85,167,156,43,291,59,
%U A120252 164,234,88,63,236,92,126,185,162,46,179,189,258,230,94,53,483,43,94
%N A120252 Number of primitive triangles with integer sides a<=b<=c and inradius n; primitive means gcd(a, b, c, n) = 1.
%C A120252 A120062(n) = sum_{k:k|n} a(k)
%D A120252 Mohammad K. Azarian, Circumradius and Inradius, Problem S125, Math Horizons, Vol. 15, Issue 4, April 2008, p. 32. Solution published in Vol. 16, Issue 2, November 2008, p. 32.
%H A120252 David W. Wilson, <a href="/A120252/b120252.txt">Table of n, a(n) for n = 1..10000</a>
%H A120252 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeronianTriangle.html">Heronian Triangle</a>
%F A120252 Moebius transform of A120062. - _David W. Wilson_, Jun 14 2006
%e A120252 a(3)= 12 because there are 12 primitive triangles with integer sides and inradius r=3. They are (10,10,12), (8,15,17), (11,13,20), (7,24,25), (8,26,30), (19,20,37), (16,25,39), (15,28,41), (13,40,51), (12,55,65), (7,65,68), (11,100,109).
%Y A120252 Cf. A120062.
%Y A120252 See A120062 for sequences related to integer-sided triangles with integer inradius n.
%K A120252 nonn
%O A120252 1,2
%A A120252 _Graeme McRae_, Jun 12 2006