A007164 Number of P-graphs with 2n edges. (Formerly M1784)

1, 2, 7, 31, 167, 999, 6495, 44619, 319463, 2356406, 17775821, 136405506, 1060866006, 8339982193, 66147792753, 528559162227, 4250413757583, 34368723106860, 279254390054538, 2278795583070154, 18667432144042678, 153452484745198722

Offset

1,2

References

R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math., 31 (1986), 47-63.

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.

Formula

a(n) = (A003169(n) + 2 * A007165(n) + A007163(n)) / 4. - Sean A. Irvine, Nov 06 2017

Crossrefs

Cf. A003169, A007163, A007165.

Sequence in context: A105216 A260532 A193657 * A321208 A005977 A199675

Adjacent sequences: A007161 A007162 A007163 * A007165 A007166 A007167

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(5), a(9), a(10) corrected and more terms from Sean A. Irvine, Nov 06 2017

Status

approved