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A068030
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Number of subsets of {1,2,3,...,n} that sum to 0 mod 9.
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2
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1, 1, 1, 1, 2, 4, 8, 15, 30, 60, 116, 230, 458, 912, 1824, 3648, 7286, 14572, 29144, 58264, 116524, 233044, 466048, 932096, 1864192, 3728300, 7456600, 14913200, 29826224, 59652440, 119304872, 238609408, 477218816, 954437632, 1908874584
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OFFSET
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0,5
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LINKS
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FORMULA
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Empirical G.f.: -(4*x^12-2*x^9-x^7+2*x^6+2*x^5+2*x^4-3*x^3-x^2-x+1) / ((2*x-1)*(2*x^3-1)*(2*x^9-1)). [Colin Barker, Dec 22 2012]
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MAPLE
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G:= Array(0..100, 0..8):
G[0, 0]:= 1; for j from 1 to 8 do G[0, j]:= 0 od:
for n from 1 to 100 do
for j from 0 to 8 do
k:= j - n mod 9;
G[n, j]:= G[n-1, j] + G[n-1, k];
od od:
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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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