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A122742 Numbers of polypentagons with two connected internal vertices (see Cyvin et al. for precise definition). 0
0, 0, 1, 3, 6, 16, 34, 80, 172, 384, 824, 1792, 3824, 8192, 17376, 36864, 77760, 163840, 343936, 720896, 1507072, 3145728, 6553088, 13631488, 28310528, 58720256, 121632768, 251658240, 520089600, 1073741824, 2214584320, 4563402752, 9395224576, 19327352832, 39728414720, 81604378624 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,4

LINKS

Table of n, a(n) for n=4..39.

S. J. Cyvin et al., Theory of polypentagons, J. Chem. Inf. Comput. Sci., 33 (1993), 466-474

Index entries for linear recurrences with constant coefficients, signature (4,-2,-8,8).

FORMULA

G.f.: x^6*(x-1)*(2*x^3-4*x^2+1) / ((2*x-1)^2*(2*x^2-1)). - Colin Barker, Aug 29 2013

a(n) = A001787(n+1)/256 - 2^(n-7) - A077957(n)/16, n>6. - R. J. Mathar, Jul 26 2019

CROSSREFS

Sequence in context: A196261 A229180 A219810 * A052370 A053304 A053305

Adjacent sequences:  A122739 A122740 A122741 * A122743 A122744 A122745

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Sep 24 2006

STATUS

approved

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Last modified October 16 20:36 EDT 2021. Contains 348047 sequences. (Running on oeis4.)