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A096302
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Number of combinations of two natural numbers that together have n digits.
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1
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81, 1620, 24300, 324000, 4050000, 48600000, 567000000, 6480000000, 72900000000, 810000000000, 8910000000000, 97200000000000, 1053000000000000, 11340000000000000, 121500000000000000, 1296000000000000000
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OFFSET
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2,1
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LINKS
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FORMULA
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a(n) = Sum_{i=0..n-1} binomial(n-1, i)*9^(i+1)*i.
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MATHEMATICA
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f[n_] := Sum[Binomial[n - 1, i]*9^(i + 1)*i, {i, 0, n}]; Table[ a[n], {n, 2, 17}] (* Robert G. Wilson v, Jun 30 2004 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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Hagai Helman (Helman(AT)actcom.net.il), Jun 25 2004
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EXTENSIONS
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STATUS
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approved
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