A339036 - OEIS

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A339036

Number of unlabeled connected loopless multigraphs with n edges rooted at one distinguished vertex.

1, 1, 3, 9, 30, 104, 390, 1518, 6208, 26372, 116221, 529341, 2487054, 12027502, 59778867, 304916272, 1594273763, 8535706749, 46753269749, 261771468438, 1497087288210, 8739579074131, 52045067963540, 315980654042243, 1954770128712348, 12315770916526091

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Table of n, a(n) for n=0..25.

FORMULA

G.f.: f(x)/g(x) where f(x) is the g.f. of A007717 and g(x) is the g.f. of A050535.

MATHEMATICA

seq[n_] := G[2n, x+O[x]^n, {1}]/G[2n, x+O[x]^n, {}] // CoefficientList[#, x]&;

seq[15] (* Jean-François Alcover, Dec 02 2020, using Andrew Howroyd's code for G in A339065 *)

PROG

(PARI) \\ See A339065 for G.