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Search: id:A114778
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| 1, 1, 2, 6, 24, 240, 4320, 120960, 9676800, 1567641600, 438939648000, 386266890240000, 750902834626560000, 2733286318040678400000, 33674087438261157888000000, 981936389699695364014080000000
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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This is the product analogue of what for sums is A114347.
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LINKS
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Eric Weisstein's World of Mathematics, Multifactorial.
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FORMULA
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a(n) = Prod[i=0 to n] n!!!. a(n) = Prod[i=0 to n] A007661(n). a(n) = n!!! * a(n-1) where a(0) = 1, a(1) = 1 and n >= 2. a(n) = n*(n-3)!!! * a(n-1) where a(0) = 1, a(1) = 1, a(2) = 2 and n >= 3.
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EXAMPLE
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a(10) = 1!!! * 2!!! * 3!!! * 4!!! * 5!!! * 6!!! * 7!!! * 8!!! * 9!!! * 10!!!
= 1 * 2 * 3 * 4 * 10 * 18 * 28 * 80 * 162 * 280 = 438939648000 = 2^15 * 3^7 * 5^3 * 7^2.
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CROSSREFS
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Cf. A006882, A000178, A114347.
Sequence in context: A052632 A052692 A052723 this_sequence A073475 A061774 A088258
Adjacent sequences: A114775 A114776 A114777 this_sequence A114779 A114780 A114781
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Feb 18 2006
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