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A014980
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Start with 5. Multiply two numbers closest to n/2 to get next number.
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3
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5, 6, 9, 20, 100, 2500, 1562500, 610351562500, 93132257461547851562500, 2168404344971008868014905601739883422851562500, 1175494350822287507968736537222245677818665556772087521508751706278417259454727172851562500
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| A194079(n) gives number of digits of a(n).
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FORMULA
| a(0) = 5; a(k+1) = floor(a(k)/2) * ceil(a(k)/2).
a(n+1) = A002620(a(n)), a(0) = 5. [Reinhard Zumkeller, Oct 12 2011]
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MATHEMATICA
| a=5; a=Table[a=Ceiling[a/2]*Floor[a/2], {n, 0, 10}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 13 2010]
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PROG
| (Haskell)
a014980 n = a014980_list !! n
a014980_list = iterate a002620 5
-- Reinhard Zumkeller, Oct 12 2011
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CROSSREFS
| Sequence in context: A117951 A124519 A154311 * A066901 A019125 A019205
Adjacent sequences: A014977 A014978 A014979 * A014981 A014982 A014983
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KEYWORD
| nonn,nice,easy
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AUTHOR
| Colin Sandon (sandon(AT)together.net)
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Feb 05 2000
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