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 A290011 #24 Jul 19 2017 14:47:02
%S A290011 6,85,900,9450,104160,1224720,15422400,207900000,2993760000,
%T A290011 45924278400,748280332800,12913284384000,235381386240000,
%U A290011 4520194398720000,91233825306624000,1931115968990208000,42778526977105920000,989887004576870400000,23885015465274163200000
%N A290011 Number of ways to connect n nodes with n+1 edges to form a 2-edge-connected graph.
%H A290011 Robert Israel, <a href="/A290011/b290011.txt">Table of n, a(n) for n = 4..448</a>
%F A290011 a(n) = (n - 4)*(n!/8) + (n*(n - 1)/2 - 3)*(n!/12) = (n^2 + 2 n - 18)*(n!/24).
%F A290011 E.g.f.: x^4*(3*x^2+x-6)/(24*(x-1)^3). - _Robert Israel_, Jul 19 2017
%p A290011 seq((n^2 + 2 *n - 18)* n!/24, n=6..30); # _Robert Israel_, Jul 19 2017
%t A290011 Table[(n - 4) (n!/8) + (n (n - 1)/2 - 3) (n!/12), {n, 4, 22}] (* _Michael De Vlieger_, Jul 18 2017 *)
%o A290011 (PARI) a(n) = (n - 4)*(n!/8) + (n*(n - 1)/2 - 3)*(n!/12); \\ _Michel Marcus_, Jul 18 2017
%Y A290011 Cf. A001072, A052447, A054596, A095983
%K A290011 easy,nonn
%O A290011 4,1
%A A290011 _Eugene Y. Q. Shen_, Jul 17 2017