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 A309150 #19 Jul 24 2019 02:53:19
%S A309150 0,2,7,12,20,29,27,41,52,60,48,101,51,96,134,93,62,142,71,209,176,114,
%T A309150 79,264,134,136,176,256,99,363,88,217,262,178,368,406,100,180,311,469,
%U A309150 119,471,113,386,508,182,116,552,223,353
%N A309150 Number of solutions of the Diophantine equation 1/n + 1/x = 1/y + 1/z, where n >= 1, x > n, y > n and z > y.
%e A309150 n=2: 1/2 + 1/12 = 1/3 + 1/4, 1/2 + 1/30 = 1/3 + 1/5.
%t A309150 a[n_]:=Length@Solve[1/(n)+1/(x)==1/y+1/z&&x>n&&z>y&&y>n,{x,y,z},Integers];
%t A309150 Array[a,50]
%Y A309150 Cf. A309149, A063647, A018892.
%K A309150 nonn
%O A309150 1,2
%A A309150 _S. Nazardonyavi_, Jul 14 2019