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 A217653 #16 Aug 14 2019 22:22:01 %S A217653 1,0,1,1,0,1,2,1,0,1,7,2,1,0,1,23,7,2,1,0,1,122,23,7,2,1,0,1,888,122, %T A217653 23,7,2,1,0,1,11302,888,122,23,7,2,1,0,1,262322,11302,888,122,23,7,2, %U A217653 1,0,1,11730500,262322,11302,888,122,23,7,2,1,0,1 %N A217653 Triangular array read by rows: T(n,k) is the number of unlabeled simple graphs with n nodes that have exactly k isolated nodes, (n>=0, 0<=k<=n). %C A217653 Row sums = A000088. %C A217653 Sum_{k=1..n} T(n,k)*k = A006897(n). %C A217653 Column k = 0 is A002494. %F A217653 O.g.f.: A(x)/(1-y*x) where A(x) is o.g.f. for A002494. %e A217653 1, %e A217653 0, 1, %e A217653 1, 0, 1, %e A217653 2, 1, 0, 1, %e A217653 7, 2, 1, 0, 1, %e A217653 23, 7, 2, 1, 0, 1, %e A217653 122, 23, 7, 2, 1, 0, 1 %t A217653 Needs["Combinatorica`"]; nn=10; s=Sum[NumberOfGraphs[n]x^n, {n,0,nn}]; CoefficientList[Series[s (1-x)/(1-y x), {x,0,nn}], {x,y}] //Grid %Y A217653 Cf. A000088, A002494, A006897. %K A217653 nonn,tabl %O A217653 0,7 %A A217653 _Geoffrey Critzer_, Oct 09 2012