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A360864
Number of unlabeled connected multigraphs with circuit rank n and degree >= 3 at each node, loops allowed.
5
0, 3, 15, 111, 1076, 13870, 220520, 4185406, 92235118, 2314204852, 65129484278, 2032179006943, 69640160993587, 2600585852722150, 105127528809344785, 4574251821427917425, 213171992131468465801, 10593983324971249199532, 559293301762878627195807, 31259896932477899016109585, 1844062168535890557437809526
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
Michael Borinsky and Karen Vogtmann, The Euler characteristic of the moduli space of graphs, arXiv:2301.01121 [math.AT], 2023.
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
KEYWORD
nonn
AUTHOR
STATUS
approved