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Search: id:A091788
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| A091788 |
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a(1) = 1, a(2) = 2 and a(n) = product of the nonzero digits of all previous terms. |
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+0
1
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| 1, 2, 2, 4, 16, 96, 5184, 829440, 1911029760, 13002646487040, 10065920762063093760, 9319918463639717615448883200, 137422208150223932126848386360776224407552000
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=a(n-1)*product of nonzero digits of a(n-1) (n>=4). - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 15 2005
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MAPLE
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p:=proc(n) local pr, nn, j: pr:=1: nn:=convert(n, base, 10): for j from 1 to nops(nn) do if nn[j]>0 then pr:=pr*nn[j] else pr:=pr: fi: od: end: a:=proc(n) if n=1 then 1 elif n=2 then 2 elif n=3 then 2 else a(n-1)*p(a(n-1)) fi end: seq(a(n), n=1..14); # p(n) is the product of the nonzero digits of n (Deutsch)
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CROSSREFS
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Sequence in context: A009542 A032318 A090753 this_sequence A063401 A129614 A070283
Adjacent sequences: A091785 A091786 A091787 this_sequence A091789 A091790 A091791
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 18 2004
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 15 2005
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