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A027809 a(n) = 143*(n+1)*C(n+4,13)/2. 1
715, 11011, 90090, 520520, 2382380, 9189180, 31039008, 94225560, 261891630, 675745070, 1636014380, 3747960216, 8180071900, 17103786700, 34420042800, 66927861000, 126159017985, 231196390425, 412918656150, 720279159600, 1229442013800, 2056876004040 (list; graph; refs; listen; history; text; internal format)
OFFSET

9,1

LINKS

T. D. Noe, Table of n, a(n) for n = 9..1000

FORMULA

Number of 18-subsequences of [ 1, n ] with just 4 contiguous pairs.

G.f.: 143*(5+2x)*x^9/(1-x)^15.

a(n) = C(n+1, 10)*C(n+4, 4). - Zerinvary Lajos, May 26 2005, corrected by R. J. Mathar, Mar 16 2016

MATHEMATICA

Table[143 (n + 1) Binomial[n + 4, 13]/2, {n, 9, 30}] (* or *) Table[Binomial[n + 1, 10] Binomial[n + 4, 4], {n, 9, 30}] (* Michael De Vlieger, Mar 16 2016 *)

CROSSREFS

Sequence in context: A255788 A029565 A154042 * A222912 A266107 A030537

Adjacent sequences:  A027806 A027807 A027808 * A027810 A027811 A027812

KEYWORD

nonn

AUTHOR

thi ngoc dinh (via R. K. Guy)

STATUS

approved

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Last modified July 16 12:38 EDT 2019. Contains 325079 sequences. (Running on oeis4.)