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A027799 a(n) = 91*(n+1)*C(n+3,14)/3. 1
364, 5915, 50960, 309400, 1485120, 5996172, 21162960, 67016040, 193993800, 520550030, 1308811504, 3109779400, 7030805600, 15210877500, 31638625200, 63520624440, 123512325300, 233272227825, 429006396000, 769953584400, 1351144354560, 2322279359400, 3915247845600 (list; graph; refs; listen; history; text; internal format)
OFFSET

11,1

COMMENTS

Number of 18-subsequences of [ 1, n ] with just 3 contiguous pairs.

LINKS

T. D. Noe, Table of n, a(n) for n = 11..1000

FORMULA

G.f.: 91*(4+x)*x^11/(1-x)^16.

a(n) = C(n+1, 12)*C(n+3, 3). - Zerinvary Lajos, May 10 2005, corrected by R. J. Mathar, Mar 16 2016

MATHEMATICA

Table[91 (n + 1) Binomial[n + 3, 14]/3, {n, 11, 33}] (* or *) Table[Binomial[n + 1, 12] Binomial[n + 3, 3], {n, 11, 33}] (* Michael De Vlieger, Mar 16 2016 *)

CROSSREFS

Sequence in context: A305184 A105920 A241617 * A115191 A175114 A022045

Adjacent sequences:  A027796 A027797 A027798 * A027800 A027801 A027802

KEYWORD

nonn,easy

AUTHOR

thi ngoc dinh (via R. K. Guy)

STATUS

approved

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Last modified February 26 09:39 EST 2020. Contains 332277 sequences. (Running on oeis4.)