A007171 Number of Q-graphs with 2n edges. (Formerly M1296)

1, 2, 4, 16, 89, 579, 3989, 28630, 210865, 1584308, 12091902, 93483120, 730503054, 5760438853, 45780146521, 366304396662, 2948412461685, 23857049238752, 193944769559906, 1583294537879106, 12974430494985262, 106685110047676402

Offset

1,2

References

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

Links

Table of n, a(n) for n=1..22.

R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math. 31 (1986) no 1, 47-63.

Formula

a(1) = 1, a(n) = A007170(n) + (A003169(n-1) + A007165(n-1)) / 2. - Sean A. Irvine, Nov 07 2017

Crossrefs

Cf. A003169, A007165, A007170.

Sequence in context: A351287 A013115 A291286 * A058136 A156335 A026089

Adjacent sequences: A007168 A007169 A007170 * A007172 A007173 A007174

Keyword

nonn,changed

Author

N. J. A. Sloane

Extensions

a(9) corrected and more terms from Sean A. Irvine, Nov 07 2017

Status

approved