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A039649
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a(n) = phi(n)+1.
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34
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2, 2, 3, 3, 5, 3, 7, 5, 7, 5, 11, 5, 13, 7, 9, 9, 17, 7, 19, 9, 13, 11, 23, 9, 21, 13, 19, 13, 29, 9, 31, 17, 21, 17, 25, 13, 37, 19, 25, 17, 41, 13, 43, 21, 25, 23, 47, 17, 43, 21, 33, 25, 53, 19, 41, 25, 37, 29, 59, 17, 61, 31, 37, 33, 49, 21, 67, 33, 45, 25, 71, 25, 73, 37, 41
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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a(p) = p for p prime.
Which n are divisible by phi(n)+1? See A085118 for a possible answer and references. - Peter Munn, Jun 03 2021
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LINKS
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FORMULA
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a(n) <= n for n > 1.
G.f.: x/(1 - x) + Sum_{k>=1} mu(k)*x^k/(1 - x^k)^2. - Ilya Gutkovskiy, Mar 16 2017
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MATHEMATICA
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PROG
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(Haskell)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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