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Search: id:A126213
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| A126213 |
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a(n) = sum of the d(k)'s, where 1<=k<=n and 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, 3, 1, 5, 1, 10, 1, 17, 7, 9, 1, 35, 1, 13, 7, 33, 1, 33, 1, 42, 7, 17, 1, 79, 6, 19, 10, 55, 1, 59, 1, 75, 10, 23, 6, 119, 1, 25, 10, 110, 1, 66, 1, 85, 24, 29, 1, 174, 1, 46, 13, 95, 1, 108, 6, 149, 13, 33, 1, 204, 1, 37, 22, 165, 6, 109, 1, 123, 13, 61, 1, 304, 1, 43, 18, 135, 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 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) = 1+2+2+2+2 = 9.
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MATHEMATICA
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f[n_] := Plus @@ Select[Table[Length@Divisors[k], {k, n}], MemberQ[Divisors[n], # ] &]; Table[f[n], {n, 78}] (*Chandler*)
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CROSSREFS
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Cf. A126212.
Sequence in context: A050329 A051707 A050354 this_sequence A133730 A112031 A046531
Adjacent sequences: A126210 A126211 A126212 this_sequence A126214 A126215 A126216
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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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