A126757 Number of n-node connected graphs with no cycles of length less than 5.

1, 1, 1, 2, 4, 8, 18, 47, 137, 464, 1793, 8167, 43645, 275480, 2045279, 17772647, 179593823, 2098423758, 28215583324, 434936005284, 7662164738118

Offset

1,4

Links

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

Keith M. Briggs, Combinatorial Graph Theory

CombOS - Combinatorial Object Server, Generate graphs

Formula

This is the inverse Euler transform of A006787. - Conjectured by Vladeta Jovovic, Jun 16 2008, proved by Max Alekseyev and Brendan McKay, Jun 17 2008

Mathematica

A006787 = Cases[Import["https://oeis.org/A006787/b006787.txt", "Table"], {_, _}][[All, 2]];
(* EulerInvTransform is defined in A022562 *)
EulerInvTransform[A006787] (* Jean-François Alcover, May 13 2019, updated Mar 17 2020 *)

Crossrefs

Cf. A006787, A140440.

Sequence in context: A252653 A006771 A113989 * A369386 A034766 A099785

Adjacent sequences: A126754 A126755 A126756 * A126758 A126759 A126760

Keyword

nonn,more

Author

N. J. A. Sloane, Feb 18 2007

Extensions

Definition corrected by Max Alekseyev and Brendan McKay, Jun 17 2008

a(20)-a(21) using Brendan McKay's extension to A006787 by Alois P. Heinz, Mar 11 2018

Status

approved