

A007168


Pgraphs with 2n edges.
(Formerly M1774)


0



1, 2, 7, 26, 114, 512, 2427, 11794, 58787, 298188, 1535962, 8009527, 42209709, 224435066, 1202611161, 6487520874, 35204691958
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OFFSET

1,2


REFERENCES

R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math., 31 (1986), 4763.
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..17.


PROG

(PARI) { s =y ; for(loop=1, 18, p = 1 ; forstep(i= 1, 2*loop1, 2, sigmai = polcoeff(s, i, y) ; n=0 ; tmp = 0 ; while(i*n <=2*loop1, ff = 1 ; for(k=1, n, ff *= (sigmaik+1)/k ; ) ; tmp += ff*(y)^(i*n) ; n++ ; ) ; p *= tmp : ) ; print1(polcoeff(p, 2*loop2, y), ", ") ; b = ys ; forstep(i=1, 2*loop1, 2, b += polcoeff(p, i, y)*y^i ; ) ; s = y ; for(r=0, loop1, for(i=0, 2*loop+1, s += polcoeff(b^(3+2*r), i, y)*y^i ; ) ; ) ; ) ; }  R. J. Mathar, Apr 24 2006


CROSSREFS

Sequence in context: A001862 A150588 A150589 * A150590 A202830 A006373
Adjacent sequences: A007165 A007166 A007167 * A007169 A007170 A007171


KEYWORD

nonn


AUTHOR

N. J. A. Sloane.


EXTENSIONS

More terms from R. J. Mathar, Apr 24 2006


STATUS

approved



