

A022562


Number of connected clawfree unlabeled graphs on n nodes.


24



1, 1, 2, 5, 14, 50, 191, 881, 4494, 26389, 184749, 1728404, 23805256, 491544474, 14491876320
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OFFSET

1,3


LINKS

Table of n, a(n) for n=1..15.
R. Faudree, E. Flandrin and Z. Ryjacek, Clawfree graphs  a survey, Discr. Math., 164 (1997), 87147.
F. Hüffner, tinygraph, software for generating integer sequences based on graph properties, version 8489dde.
Gordon Royle, 1728404 distinct 12vertex connected clawfree graphs
Gordon Royle, g6 format
Eric Weisstein's World of Mathematics, ClawFree Graph
Wikipedia, Clawfree Graph


FORMULA

Inverse Euler transform of A086991.  Andrew Howroyd, Nov 03 2017


MATHEMATICA

EulerInvTransform[seq_] := Module[{final = {}}, For[i = 1, i <= Length[seq], i++, AppendTo[final, i*seq[[i]]  Sum[final[[d]]*seq[[i  d]], {d, i  1}]]]; Table[Sum[MoebiusMu[i/d]*final[[d]], {d, Divisors[i]}]/i, {i, Length[seq]}]];
A086991 = Cases[Import["https://oeis.org/A086991/b086991.txt", "Table"], {_, _}][[All, 2]];
EulerInvTransform[A086991] (* JeanFrançois Alcover, Aug 20 2019, code due to Gus Wiseman *)


CROSSREFS

Cf. A022563, A022564, A058929, A086991 (Euler transform).
Sequence in context: A224978 A006390 A100597 * A320954 A322725 A245883
Adjacent sequences: A022559 A022560 A022561 * A022563 A022564 A022565


KEYWORD

nonn,nice,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Corrected and extended by Gordon F. Royle, May 16 2003
Term a(14) added by Gordon F. Royle, Aug 06 2008
Term a(15) added using tinygraph by Falk Hüffner, Jan 12 2016


STATUS

approved



