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Search: id:A139130
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| A139130 |
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a(n) = sum{k=1 to n} d(d(k)), where d(k) = number of divisors of k. |
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+0
1
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| 1, 3, 5, 7, 9, 12, 14, 17, 19, 22, 24, 28, 30, 33, 36, 38, 40, 44, 46, 50, 53, 56, 58, 62, 64, 67, 70, 74, 76, 80, 82, 86, 89, 92, 95, 98, 100, 103, 106, 110, 112, 116, 118, 122, 126, 129, 131, 135, 137, 141, 144, 148, 150, 154, 157, 161, 164, 167, 169, 175, 177, 180
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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R. Bellman and H. N. Shapiro, On a problem in additive number theory, Annals Math., 49 (1948), 333-340. See Eq. 1.6. [From N. J. A. Sloane, Mar 12 2009]
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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MAPLE
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with (numtheory): a:= n-> add (tau (tau (k)), k=1..n): seq (a(n), n=1..70); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 28 2008]
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CROSSREFS
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Cf. A010553, A006218.
Sequence in context: A033036 A082767 A047932 this_sequence A072154 A080751 A025218
Adjacent sequences: A139127 A139128 A139129 this_sequence A139131 A139132 A139133
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jun 05 2008
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EXTENSIONS
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More terms from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 28 2008
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