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Search: id:A161946
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| A161946 |
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Odd part of sum of unitary divisors of n. |
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+0
2
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| 1, 3, 1, 5, 3, 3, 1, 9, 5, 9, 3, 5, 7, 3, 3, 17, 9, 15, 5, 15, 1, 9, 3, 9, 13, 21, 7, 5, 15, 9, 1, 33, 3, 27, 3, 25, 19, 15, 7, 27, 21, 3, 11, 15, 15, 9, 3, 17, 25, 39, 9, 35, 27, 21, 9, 9, 5, 45, 15, 15, 31, 3, 5, 65, 21, 9, 17, 45, 3, 9, 9, 45, 37, 57, 13, 25, 3, 21, 5, 51, 41, 63, 21, 5, 27
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Since a(n) < n for any odd n > 1, iterating this function always leads to 1.
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FORMULA
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Multiplicative with a(p^e) = oddpart(p^e+1), where oddpart(n) = A000265(n) is the largest odd divisor of n.
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PROGRAM
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(PARI) oddpart(n)=n/2^valuation(n, 2)
a(n)=local(fm, r); fm=factor(n); r=1; for(k=1, matsize(fm)[1], r*=oddpart(fm[k, 1]^fm[k, 2]+1)); r
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CROSSREFS
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Cf. A161942, A034448, A151659.
Sequence in context: A060439 A135224 A152203 this_sequence A013597 A092131 A092099
Adjacent sequences: A161943 A161944 A161945 this_sequence A161947 A161948 A161949
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KEYWORD
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easy,mult,nonn
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AUTHOR
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Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Jun 22 2009
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