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A027781 4*(n+1)*C(n+2,8). 0
28, 288, 1620, 6600, 21780, 61776, 156156, 360360, 772200, 1555840, 2975544, 5441904, 9573720, 16279200, 26860680, 43147632, 67663332, 103831200, 156227500, 230887800, 335675340, 480720240, 678939300 (list; graph; refs; listen; history; text; internal format)
OFFSET

6,1

LINKS

Table of n, a(n) for n=6..28.

Index entries for linear recurrences with constant coefficients, signature (10,-45,120,-210,252,-210,120,-45,10,-1)

FORMULA

Number of 11-subsequences of [ 1, n ] with just 2 contiguous pairs; g.f. 4*(7+2*x)*x^6/(1-x)^10.

a(n) = C(n+1, 7)*C(n+2, 2). - Zerinvary Lajos, May 13 2005

a(6)=28, a(7)=288, a(8)=1620, a(9)=6600, a(10)=21780, a(11)=61776, a(12)=156156, a(13)=360360, a(14)=772200, a(15)=1555840, a(n)= 10*a(n-1)- 45*a(n-2) +120*a(n-3) -210*a(n-4) +252*a(n-5) -210*a(n-6) +120*a(n-7) -45*a(n-8) +10*a(n-9) -a(n-10). - Harvey P. Dale, May 20 2012

MATHEMATICA

Drop[Table[4(n+1)Binomial[n+2, 8], {n, 30}], 5] (* or *) LinearRecurrence[ {10, -45, 120, -210, 252, -210, 120, -45, 10, -1}, {28, 288, 1620, 6600, 21780, 61776, 156156, 360360, 772200, 1555840}, 30] (* Harvey P. Dale, May 20 2012 *)

CROSSREFS

Sequence in context: A107418 A183484 A241621 * A219626 A126662 A156711

Adjacent sequences:  A027778 A027779 A027780 * A027782 A027783 A027784

KEYWORD

nonn,easy

AUTHOR

thi ngoc dinh (via R. K. Guy)

EXTENSIONS

Offset corrected by Harvey P. Dale, May 20 2012

STATUS

approved

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Last modified June 21 12:19 EDT 2021. Contains 345364 sequences. (Running on oeis4.)