login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A023582 Number of distinct prime divisors of 2*prime(n)-1. 2
1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 1, 2, 2, 3, 2, 1, 2, 2, 2, 1, 3, 2, 1, 2, 2, 2, 2, 2, 2, 2, 3, 1, 2, 2, 1, 2, 2, 3, 3, 1, 2, 3, 2, 1, 1, 2, 2, 1, 3, 2, 2, 2, 2, 3, 2, 1, 2, 3, 2, 3, 1, 2, 1, 2, 1, 1, 3, 2, 3, 2, 1, 2, 1, 3, 3, 2, 2, 2, 2, 1, 3, 2, 1, 3, 3, 2, 2, 2, 2, 3, 2, 2, 1, 3, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = A001221(A076274(n)). - Michel Marcus, Oct 01 2013

MAPLE

seq(nops(numtheory:-factorset(2*ithprime(n)-1)), n=1..120); # Muniru A Asiru, Apr 29 2019

MATHEMATICA

PrimeNu[2*Prime[Range[100]]-1] (* Harvey P. Dale, Jan 25 2015 *)

PROG

(PARI) a(n) = omega(2*prime(n)-1); \\ Michel Marcus, Oct 01 2013

CROSSREFS

Sequence in context: A206828 A327164 A094781 * A306717 A195969 A023518

Adjacent sequences:  A023579 A023580 A023581 * A023583 A023584 A023585

KEYWORD

nonn

AUTHOR

Clark Kimberling

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 June 23 18:45 EDT 2021. Contains 345402 sequences. (Running on oeis4.)