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A034689 a(n) = n-th sextic factorial number divided by 2. 13
1, 8, 112, 2240, 58240, 1863680, 70819840, 3116072960, 155803648000, 8725004288000, 540950265856000, 36784618078208000, 2722061737787392000, 217764939022991360000, 18727784755977256960000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..15.

FORMULA

2*a(n) = (6*n-4)(!^6) = product_{j=1..n} (6*j-4) = 2^n*A007559(n), A007559(n) = (3*n-2)(!^3) = product_{j=1..n} (3*j-2).

E.g.f. (-1 + (1-6*x)^(-1/3))/2).

MATHEMATICA

s=1; lst={s}; Do[s+=n*s; AppendTo[lst, s], {n, 7, 5!, 6}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008 *)

CROSSREFS

Cf. A008542, A007559.

Sequence in context: A265665 A302104 A219184 * A010041 A099703 A296467

Adjacent sequences:  A034686 A034687 A034688 * A034690 A034691 A034692

KEYWORD

easy,nonn

AUTHOR

Wolfdieter Lang

STATUS

approved

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Last modified October 19 19:55 EDT 2018. Contains 316378 sequences. (Running on oeis4.)