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A066263 2^n+1 has just two distinct prime factors. 1
5, 6, 7, 9, 10, 11, 12, 13, 17, 19, 20, 23, 28, 31, 32, 40, 43, 61, 64, 79, 92, 101, 104, 127, 128, 148, 167, 191, 199, 313, 347, 356, 596, 692, 701, 1004, 1228, 1268 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

LINKS

Samuel S. Wagstaff, The Cunningham Project

MATHEMATICA

f[n_] := First[ Transpose[ FactorInteger[2^n + 1, FactorComplete -> True]]]; Select[ Range[100], Length[f[ # ]] == 2 & ]

CROSSREFS

Cf. A073936.

Sequence in context: A205857 A196026 A191850 * A178096 A089192 A132829

Adjacent sequences:  A066260 A066261 A066262 * A066264 A066265 A066266

KEYWORD

nonn

AUTHOR

Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 31 2001

EXTENSIONS

Edited by Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 03 2002

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Last modified February 16 02:30 EST 2012. Contains 205860 sequences.