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 A215773 #7 Aug 23 2012 21:07:30 %S A215773 0,3,25,120,420,1190,2898,6300,12540,23265,40755,68068,109200,169260, %T A215773 254660,373320,534888,750975,1035405,1404480,1877260,2475858,3225750, %U A215773 4156100,5300100,6695325,8384103,10413900,12837720,15714520,19109640,23095248,27750800 %N A215773 Number of undirected labeled graphs on n+3 nodes with exactly n cycle graphs as connected components. %H A215773 Alois P. Heinz, <a href="/A215773/b215773.txt">Table of n, a(n) for n = 0..1000</a> %F A215773 G.f.: (8*x^2+4*x+3)*x/(1-x)^7. %F A215773 a(n) = n*(n+1)*(n+2)*(n+3)*(n^2+n+4)/48. %e A215773 a(1) = 3: .1-2. .1.2. .1-2. %e A215773 . .|.|. .|X|. ..X.. %e A215773 . .3-4. .3.4. .3-4. %p A215773 a:= n-> (24+(50+(41+(21+(7+n)*n)*n)*n)*n)*n/48: %p A215773 seq (a(n), n=0..40); %Y A215773 A diagonal of A215771. %K A215773 nonn %O A215773 0,2 %A A215773 _Alois P. Heinz_, Aug 23 2012