A165318 Primes p where the number of divisors of p-1 is a power of 2.

2, 3, 7, 11, 23, 31, 41, 43, 47, 59, 67, 71, 79, 83, 89, 103, 107, 131, 137, 139, 167, 179, 191, 211, 223, 227, 233, 239, 251, 263, 271, 281, 283, 311, 313, 331, 347, 359, 367, 379, 383, 409, 419, 431, 439, 443, 457, 463, 467, 479, 499, 503, 521, 547, 563, 569

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Maple

isA000079 := proc(n) RETURN( n=1 or numtheory[factorset](n) = {2}) ; end: A165318 := proc(n) if n = 1 then 2; else p := nextprime(procname(n-1)) ; while not isA000079(numtheory[tau](p-1)) do p := nextprime(p) ; od; p ; fi; end: seq(A165318(n), n=1..90) ; # R. J. Mathar, Sep 18 2009

Mathematica

Select[Prime[Range[200]], IntegerQ[Log[2, DivisorSigma[0, #-1]]]&] (* Harvey P. Dale, Oct 14 2018 *)

Crossrefs

Cf. A165319, A165320.

Sequence in context: A126755 A228592 A034795 * A108184 A049091 A039787

Adjacent sequences: A165315 A165316 A165317 * A165319 A165320 A165321

Keyword

nonn

Author

Leroy Quet, Sep 14 2009

Extensions

More terms from R. J. Mathar, Sep 18 2009

Status

approved