A007171 Number of Q-graphs with 2n edges.
1, 2, 4, 16, 89, 579, 3989, 28630, 210865, 1584308, 12091902, 93483120, 730503054, 5760438853, 45780146521, 366304396662, 2948412461685, 23857049238752, 193944769559906, 1583294537879106, 12974430494985262, 106685110047676402
Offset: 1
Keywords
References
- N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Links
- R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math. 31 (1986) no 1, 47-63.
Formula
Extensions
a(9) corrected and more terms from Sean A. Irvine, Nov 07 2017