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A113999
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a(n) = Sum_{ k, k|n } 10^(k-1).
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9
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1, 11, 101, 1011, 10001, 100111, 1000001, 10001011, 100000101, 1000010011, 10000000001, 100000101111, 1000000000001, 10000001000011, 100000000010101, 1000000010001011, 10000000000000001, 100000000100100111
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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G.f.: Sum_{n>0} x^n/(1-10*x^n).
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PROG
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(PARI) a(n)=if(n<1, 0, sumdiv(n, k, 10^(k-1)));
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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