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A027812 a(n) = 7*(n+1)*C(n+5,7). 0
21, 224, 1260, 5040, 16170, 44352, 108108, 240240, 495495, 960960, 1769768, 3118752, 5290740, 8682240, 13837320, 21488544, 32605881, 48454560, 70662900, 101301200, 142972830, 198918720, 273136500, 370515600, 496989675 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..26.

Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1).

FORMULA

Number of 13-subsequences of [ 1, n ] with just 5 contiguous pairs; g.f. 7*(3+5x)*x^2/(1-x)^9.

a(n) = C(n+1, 3)*C(n+5, 5). - Zerinvary Lajos, May 26 2005, corrected by R. J. Mathar, Feb 10 2016

CROSSREFS

Sequence in context: A134585 A165402 A135120 * A171112 A171108 A219439

Adjacent sequences:  A027809 A027810 A027811 * A027813 A027814 A027815

KEYWORD

nonn

AUTHOR

thi ngoc dinh (via R. K. Guy)

STATUS

approved

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Last modified August 4 12:45 EDT 2020. Contains 336201 sequences. (Running on oeis4.)