A007163 Number of P-graphs with vertical symmetry. (Formerly M2854)

1, 3, 10, 39, 158, 674, 2944, 13191, 60078, 277890, 1300536, 6151078, 29346036, 141088632, 682825140, 3324172359, 16267134462, 79975707362, 394833880540, 1956620531762, 9729300574580, 48529814786620, 242757311049680, 1217508537475894

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..24.

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

Formula

a(n) = coefficient of x^(2*n) in D(x)^2 / (1-D(x)^2) where D(x) = Sum_{k=0..infinity} A007162(k) * x^(2*k+1). - Sean A. Irvine, Nov 06 2017

Crossrefs

Cf. A007162.

Sequence in context: A151065 A151066 A151067 * A219263 A050385 A296195

Adjacent sequences: A007160 A007161 A007162 * A007164 A007165 A007166

Keyword

nonn

Author

N. J. A. Sloane

Extensions

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

Status

approved