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Search: id:A126132
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| A126132 |
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a(n) = number of k's, 1<=k<=n, where d(k) is equal to any divisor of n, where d(k) is the number of positive divisors of k. |
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+0
2
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| 1, 2, 1, 3, 1, 5, 1, 7, 3, 5, 1, 12, 1, 7, 3, 12, 1, 12, 1, 15, 3, 9, 1, 23, 2, 10, 4, 19, 1, 19, 1, 23, 4, 12, 2, 33, 1, 13, 4, 31, 1, 22, 1, 29, 6, 15, 1, 45, 1, 18, 5, 32, 1, 31, 2, 40, 5, 17, 1, 53, 1, 19, 6, 45, 2, 33, 1, 41, 5, 23, 1, 69, 1, 22, 6, 45, 2, 39, 1, 59, 6, 23, 1, 70, 3, 24, 5
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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 terms of the sequence of the first ten d(k)'s which equal any divisor of 10 are the five terms 1,2,2,2,2. So a(10) = 5.
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MATHEMATICA
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f[n_] := Length@Select[Table[Length@Divisors[k], {k, n}], MemberQ[Divisors[n], # ] &]; Table[f[n], {n, 87}] (*Chandler*)
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CROSSREFS
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Cf. A126131.
Sequence in context: A130008 A101809 A127203 this_sequence A129982 A052552 A085053
Adjacent sequences: A126129 A126130 A126131 this_sequence A126133 A126134 A126135
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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 18 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 20 2006
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