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Search: id:A126212
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| A126212 |
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a(n) = sum of the divisors of n which equal any d(k) for 1<=k<=n, where d(k) is the number of positive divisors of k. |
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+0
2
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| 1, 3, 1, 3, 1, 6, 1, 7, 4, 3, 1, 16, 1, 3, 4, 7, 1, 12, 1, 12, 4, 3, 1, 24, 6, 3, 4, 7, 1, 17, 1, 15, 4, 3, 6, 25, 1, 3, 4, 20, 1, 12, 1, 7, 18, 3, 1, 24, 1, 18, 4, 7, 1, 21, 6, 15, 4, 3, 1, 43, 1, 3, 13, 15, 6, 12, 1, 7, 4, 25, 1, 45, 1, 3, 9, 7, 8, 12, 1, 30, 13, 3, 1, 35, 6, 3, 4, 15, 1, 36, 8
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OFFSET
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1,2
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EXAMPLE
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The number of divisors of the integers 1 through 10 form the sequence 1,2,2,3,2,4,2,4,3,4. The divisors of 10 are 1,2,5,10. The divisors of 10 which occur in the sequence of d(k)'s, 1<=k<=10, are 1 and 2. So a(10) = 1+2 = 3.
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MATHEMATICA
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f[n_] :=Plus @@ Select[Divisors[n], MemberQ[Table[Length@Divisors[k], {k, n}], # ] &]; Table[f[n], {n, 91}] (*Chandler*)
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CROSSREFS
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Cf. A126213.
Sequence in context: A053575 A103790 A013603 this_sequence A066637 A050336 A095250
Adjacent sequences: A126209 A126210 A126211 this_sequence A126213 A126214 A126215
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Dec 20 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 21 2006
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