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A125747
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a(n) is the smallest positive integer such that (sum{t(k)|n, 1<=k<=a(n)} t(k)) is >= n, where t(k) is the k-th positive divisor of n..
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2
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1, 2, 2, 3, 2, 3, 2, 4, 3, 4, 2, 5, 2, 4, 4, 5, 2, 5, 2, 5, 4, 4, 2, 6, 3, 4, 4, 5, 2, 7, 2, 6, 4, 4, 4, 7, 2, 4, 4, 7, 2, 7, 2, 6, 6, 4, 2, 8, 3, 6, 4, 6, 2, 7, 4, 7, 4, 4, 2, 10, 2, 4, 6, 7, 4, 7, 2, 6, 4, 7, 2, 10, 2, 4, 6, 6, 4, 7, 2, 9, 5, 4, 2, 10, 4, 4, 4, 7, 2, 10, 4, 6, 4, 4, 4, 10, 2, 6, 6, 8, 2, 7, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| The divisors of 12 are 1,2,3,4,6,12. 1+2+3+4 = 10, which is smaller than 12; but 1+2+3+4+6 = 16, which is >= 12. 6 is the 5th divisor of 12, so a(12) = 5.
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MATHEMATICA
| f[n_] := Block[{k = 1, d = Divisors[n]}, While[Sum[d[[i]], {i, k}] < n, k++ ]; k]; Table[f[n], {n, 105}] (*Chandler*)
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CROSSREFS
| Cf. A125746, A117553.
Sequence in context: A166469 A080226 A060741 * A060129 A173908 A054030
Adjacent sequences: A125744 A125745 A125746 * A125748 A125749 A125750
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Dec 05 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 06 2006
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