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A206244
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Number of partitions of n into repunits (A002275).
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3
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8
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OFFSET
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0,12
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COMMENTS
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LINKS
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Eric Weisstein's World of Mathematics, Repunit
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FORMULA
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G.f.: Product_{k>=1} 1/(1 - x^((10^k-1)/9)). - Ilya Gutkovskiy, Jul 26 2017
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EXAMPLE
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a(12)=2 is the first nontrivial term, from the partitions 12 = 1+1+...+1 = 11+1. - N. J. A. Sloane, Jul 26 2017
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MATHEMATICA
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With[{nn = 50}, Table[Count[IntegerPartitions@ n, k_ /; ContainsAll[Array[Floor[10^#/9] &, IntegerLength[nn + 1]], Union@ k]], {n, 0, nn}]] (* Michael De Vlieger, Jul 26 2017 *)
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PROG
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(Haskell)
a206244 = p $ tail a002275_list where
p _ 0 = 1
p rus'@(ru:rus) n = if n < ru then 0 else p rus' (n - ru) + p rus n
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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