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A084949 a(n) = product_{i=0..n-1} (9*i+2). 13
1, 2, 22, 440, 12760, 484880, 22789360, 1276204160, 82953270400, 6138542009600, 509498986796800, 46873906785305600, 4734264585315865600, 520769104384745216000, 61971523421784680704000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Robert Israel, Table of n, a(n) for n = 0..329

FORMULA

a(n) = A084944(n)/A000142(n)*A000079(n) = 9^n*pochhammer(2/9, n) = 9^n*GAMMA(n+2/9)/GAMMA(2/9).

a(n) = (-7)^n*sum_{k=0..n} (9/7)^k*s(n+1,n+1-k), where s(n,k) are the Stirling numbers of the first kind, A048994. - Mircea Merca, May 03 2012

E.g.f.: (1-9x)^(-2/9). - Robert Israel, Mar 22 2017

MAPLE

a := n->product(9*i+2, i=0..n-1); [seq(a(j), j=0..30)];

MATHEMATICA

s=1; lst={s}; Do[s+=n*s; AppendTo[lst, s], {n, 1, 2*5!, 9}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008 *)

CROSSREFS

Cf. A000165, A008544, A001813, A047055, A047657, A084947, A084948.

Cf. A035012.

Sequence in context: A241347 A163436 A266522 * A276454 A137076 A090730

Adjacent sequences:  A084946 A084947 A084948 * A084950 A084951 A084952

KEYWORD

easy,nonn

AUTHOR

Daniel Dockery (peritus(AT)gmail.com), Jun 13 2003

STATUS

approved

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Last modified March 23 14:17 EDT 2019. Contains 321431 sequences. (Running on oeis4.)