A122742 Numbers of polypentagons with two connected internal vertices (see Cyvin et al. for precise definition).

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

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: A229180 A219810 A364319 * A052370 A053304 A053305

Adjacent sequences: A122739 A122740 A122741 * A122743 A122744 A122745

Keyword

nonn,easy

Author

N. J. A. Sloane, Sep 24 2006

Status

approved