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A287891 Number of rooted unlabeled 4-cactus graphs on 3n+1 nodes. 5
1, 1, 3, 11, 46, 208, 1002, 5012, 25863, 136519, 733902, 4003475, 22106155, 123313289, 693871975, 3933700703, 22447035938, 128828019447, 743142630614, 4306327193744, 25056121416684, 146325789652514, 857393585946194, 5039223717251954, 29700183601347111, 175496470696059267 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..500

Maryam Bahrani and Jérémie Lumbroso, Enumerations, Forbidden Subgraph Characterizations, and the Split-Decomposition, arXiv:1608.01465 [math.CO], 2016.

PROG

(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}

seq(n)={my(v=[]); for(n=1, n, my(g=1+x*Ser(v)); v=EulerT(Vec(g*(g^2 + subst(g, x, x^2))/2))); concat([1], v)} \\ Andrew Howroyd, Feb 17 2020

CROSSREFS

Column k=4 of A332648.

Cf. A003080, A287889, A287890, A287892.

Sequence in context: A006605 A306822 A193074 * A233389 A281548 A086521

Adjacent sequences:  A287888 A287889 A287890 * A287892 A287893 A287894

KEYWORD

nonn,changed

AUTHOR

N. J. A. Sloane, Jun 21 2017

EXTENSIONS

a(0) changed and terms a(11) and beyond from Andrew Howroyd, Feb 17 2020

STATUS

approved

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Last modified February 24 03:22 EST 2020. Contains 332195 sequences. (Running on oeis4.)