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A085118 Primes together with twice the odd primes. 1
2, 3, 5, 6, 7, 10, 11, 13, 14, 17, 19, 22, 23, 26, 29, 31, 34, 37, 38, 41, 43, 46, 47, 53, 58, 59, 61, 62, 67, 71, 73, 74, 79, 82, 83, 86, 89, 94, 97, 101, 103, 106, 107, 109, 113, 118, 122, 127, 131, 134, 137, 139, 142, 146, 149, 151, 157, 158, 163, 166, 167, 173, 178 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Probably the same sequence as: numbers n such that phi(n)+1 divides n.

Cohen and Segal showed that in case there were other solutions to this problem (which appeared to be posed by Schinzel), then they should have at least 15 distinct prime factors. Moreover, there is a connection with the Lehmer's totient problem which asks whether there is a composite n such that phi(n)|(n-1). If no such composite exists, then p and 2p are the only members for Leroy's sequence. - Francisco Salinas (franciscodesalinas(AT)hotmail.com), Apr 25 2004

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

G. L. Cohen, S. L. Segal, A note concerning those n for which phi(n)+1 divides n, Fibonacci Quarterly 27 (1989), no. 3, pp. 285-286.

Eric Weisstein's World of Mathematics, Lehmer's Totient Problem

MATHEMATICA

With[{nn=40}, Take[Sort[Join[Prime[Range[2nn]], 2Prime[Range[2, nn]]]], 2nn]] (* Harvey P. Dale, Oct 03 2013 *)

CROSSREFS

Cf. A068422.

Sequence in context: A326533 A144147 A068422 * A276579 A166158 A289997

Adjacent sequences:  A085115 A085116 A085117 * A085119 A085120 A085121

KEYWORD

nonn,easy

AUTHOR

Leroy Quet, Apr 25 2004

EXTENSIONS

More terms from David Wasserman, Jan 27 2005

STATUS

approved

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Last modified September 17 11:03 EDT 2019. Contains 327129 sequences. (Running on oeis4.)