A360864 - OEIS

A360864

Number of unlabeled connected multigraphs with circuit rank n and degree >= 3 at each node, loops allowed.

0, 3, 15, 111, 1076, 13870, 220520, 4185406, 92235118, 2314204852, 65129484278, 2032179006943, 69640160993587, 2600585852722150, 105127528809344785, 4574251821427917425, 213171992131468465801, 10593983324971249199532, 559293301762878627195807, 31259896932477899016109585, 1844062168535890557437809526

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OFFSET

1,2

COMMENTS

The terms up to a(21) were computed by Michael Borinsky and Jos Vermaseren using a program written in FORM. The graphs enumerated by a(n) are called admissible (Borinsky and Vogtmann, 2023).

LINKS

Table of n, a(n) for n=1..21.

Michael Borinsky and Karen Vogtmann, The Euler characteristic of the moduli space of graphs, arXiv:2301.01121 [math.AT], 2023.

Tony Guttmann, Asymptotics for A360864

Leila Sloman, Quantum Field Theory Pries Open Mathematical Puzzle, Quanta Magazine, Feb 2023.

FORMULA

a(n) = Sum_{k>=1} A360862(n + k - 1, k).

CROSSREFS

Diagonal sums of A360862.

Sequence in context: A089468 A109498 A142967 * A201339 A370877 A375905

Adjacent sequences: A360861 A360862 A360863 * A360865 A360866 A360867

KEYWORD

nonn

AUTHOR

Andrew Howroyd and William P. Orrick, Feb 24 2023

STATUS

approved