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Search: id:A007168
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| A007168 |
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P-graphs with 2n edges.
(Formerly M1774)
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+0
1
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| 1, 2, 7, 26, 114, 512, 2427, 11794, 58787, 298188, 1535962, 8009527, 42209709, 224435066, 1202611161, 6487520874, 35204691958
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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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).
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PROGRAM
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(PARI) { s =y ; for(loop=1, 18, p = 1 ; forstep(i= 1, 2*loop-1, 2, sigmai = polcoeff(s, i, y) ; n=0 ; tmp = 0 ; while(i*n <=2*loop-1, ff = 1 ; for(k=1, n, ff *= (-sigmai-k+1)/k ; ) ; tmp += ff*(-y)^(i*n) ; n++ ; ) ; p *= tmp : ) ; print1(polcoeff(p, 2*loop-2, y), ", ") ; b = y-s ; forstep(i=1, 2*loop-1, 2, b += polcoeff(p, i, y)*y^i ; ) ; s = y ; for(r=0, loop-1, for(i=0, 2*loop+1, s += polcoeff(b^(3+2*r), i, y)*y^i ; ) ; ) ; ) ; } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 24 2006
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CROSSREFS
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Sequence in context: A001862 A150588 A150589 this_sequence A150590 A006373 A030429
Adjacent sequences: A007165 A007166 A007167 this_sequence A007169 A007170 A007171
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 24 2006
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