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A034723
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One third of sextic factorial numbers.
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7
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1, 9, 135, 2835, 76545, 2525985, 98513415, 4433103675, 226088287425, 12887032383225, 811883040143175, 56019929769879075, 4201494732740930625, 340321073352015380625, 29607933381625338114375
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| 3*a(n) = (6*n-3)(!^6) := product(6*j-3, j=1..n) = 3^n*A001147(n) = 3^n*(2*n)!/(2^n*n!), A001147(n)=(2*n-1)!!; E.g.f. (-1+(1-6*x)^(-1/2))/3.
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MATHEMATICA
| s=1; lst={s}; Do[s+=n*s; AppendTo[lst, s], {n, 8, 5!, 6}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 08 2008]
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CROSSREFS
| Cf. A008542, A034689.
Sequence in context: A112426 A163200 A167893 * A188685 A052137 A003376
Adjacent sequences: A034720 A034721 A034722 * A034724 A034725 A034726
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KEYWORD
| easy,nonn
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de)
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