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A039649 a(n) = phi(n)+1. 33
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)
OFFSET
1,1
COMMENTS
a(p) = p for p prime.
Records give A000040. - Omar E. Pol, Jul 10 2014
Which n are divisible by phi(n)+1? See A085118 for a possible answer and references. - Peter Munn, Jun 03 2021
LINKS
N. J. A. Sloane, Families of Essentially Identical Sequences, Mar 24 2021 (Includes this sequence)
FORMULA
a(n) = A000010(n) + 1.
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
MATHEMATICA
Table[EulerPhi[n] + 1, {n, 100}] (* Vincenzo Librandi, Aug 13 2013 *)
PROG
(Magma) [EulerPhi(n)+1: n in [1..100]]; // Vincenzo Librandi, Aug 13 2013
(Haskell)
a039649 = (+ 1) . a000010 -- Reinhard Zumkeller, Oct 07 2015
(PARI) a(n)=eulerphi(n)+1 \\ Charles R Greathouse IV, Mar 04 2017
CROSSREFS
Sequence in context: A263027 A069974 A039650 * A214288 A332825 A253554
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Edited by Charles R Greathouse IV, Mar 18 2010.
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)