The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A322140 Number of labeled 2-connected multigraphs with n edges (the vertices are {1,2,...,k} for some k). 2
 1, 1, 1, 2, 7, 37, 262, 2312, 24338, 296928, 4112957, 63692909, 1089526922, 20389411551, 414146189901, 9070116944468, 212983762029683, 5336570227705763, 142083405456873290, 4004953714929148655, 119128974685786590410, 3728639072095285867881 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS We consider a single edge to be 2-connected, so a(1) = 1. LINKS Andrew Howroyd, Table of n, a(n) for n = 0..100 PROG (PARI) seq(n)={Vec(1 + vecsum(Vec(serlaplace(log(x/serreverse(x*deriv(log(sum(k=0, n, 1/(1 - y + O(y*y^n))^binomial(k, 2) * x^k / k!) + O(x*x^n)))))))))} \\ Andrew Howroyd, Nov 29 2018 CROSSREFS Cf. A002218, A002905, A013922, A275307, A291841, A304118, A304887, A322110, A322117, A322118, A322137, A322138. Sequence in context: A135164 A321087 A072597 * A125515 A135920 A001515 Adjacent sequences:  A322137 A322138 A322139 * A322141 A322142 A322143 KEYWORD nonn AUTHOR Gus Wiseman, Nov 27 2018 EXTENSIONS Terms a(7) and beyond from Andrew Howroyd, Nov 29 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 29 12:15 EDT 2020. Contains 337431 sequences. (Running on oeis4.)