login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A165318 Primes p where the number of divisors of p-1 is a power of 2. 3
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 21 00:08 EST 2019. Contains 329348 sequences. (Running on oeis4.)