A007100 Number of labeled trivalent (or cubic) 3-connected graphs with 2n nodes. (Formerly M5343)

1, 70, 16800, 9238320, 9520156800, 16305064776000, 42856575521760000, 163329351308323200000, 864876880105205071104000, 6155146233167046820024320000, 57316399761348433188962519040000

Offset

2,2

References

R. W. Robinson, personal communication.

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

R. W. Robinson, Table of n, a(n) for n = 2..28

R. W. Robinson, Cubic labeled graphs, computer print-out, n.d. (see last page)

Formula

a(n) = (2*n)!*r(n)/(3*n*2^n) where r(2) = 1 and r(n) = (3*n-2) * (r(n-1) + Sum_{i=2..n-2} r(i) * r(n-i)). - Sean A. Irvine, Oct 11 2017

Crossrefs

Sequence in context: A229776 A362169 A231054 * A103157 A364305 A007099

Adjacent sequences: A007097 A007098 A007099 * A007101 A007102 A007103

Keyword

nonn

Author

N. J. A. Sloane

Status

approved