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A126131
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a(n) = number of 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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3
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1, 2, 1, 2, 1, 3, 1, 3, 2, 2, 1, 5, 1, 2, 2, 3, 1, 4, 1, 4, 2, 2, 1, 6, 2, 2, 2, 3, 1, 5, 1, 4, 2, 2, 2, 6, 1, 2, 2, 5, 1, 4, 1, 3, 4, 2, 1, 6, 1, 4, 2, 3, 1, 5, 2, 4, 2, 2, 1, 8, 1, 2, 3, 4, 2, 4, 1, 3, 2, 5, 1, 8, 1, 2, 3, 3, 2, 4, 1, 6, 3, 2, 1, 7, 2, 2, 2, 4, 1, 7, 2, 3, 2, 2, 2, 7, 1, 3, 3, 5, 1, 4, 1, 4, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| 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) = 2.
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MATHEMATICA
| f[n_] :=Length@Select[Divisors[n], MemberQ[Table[Length@Divisors[k], {k, n}], # ] &]; Table[f[n], {n, 105}] (*Chandler*)
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CROSSREFS
| Cf. A126132.
Sequence in context: A027353 A027352 A029238 * A138012 A072531 A025818
Adjacent sequences: A126128 A126129 A126130 * A126132 A126133 A126134
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet, Dec 18 2006
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 20 2006
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