A007163 - OEIS

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

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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