A007170 Number of Q-graphs with 2n edges. (Formerly M1877)

0, 1, 2, 8, 48, 328, 2335, 17133, 128262, 975547, 7518282, 58582564, 460769228, 3653385453, 29170737927, 234350263419, 1892956305974, 15364355580327, 125247311808502, 1024983176867450, 8417817643684208, 69355110426227296

Offset

1,3

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(n) = A007169(n) + (A294724(n) - A294728(n)) / 2. - Sean A. Irvine, Nov 07 2017

Crossrefs

Cf. A007169, A294724, A294728.

Sequence in context: A356429 A391455 A228568 * A355488 A379382 A171455

Adjacent sequences: A007167 A007168 A007169 * A007171 A007172 A007173

Keyword

nonn,changed

Author

N. J. A. Sloane

Extensions

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

Status

approved