A115973 - OEIS

A115973

Number of distinct prime factors of p^p + 1 where p is prime(n).

1, 2, 3, 3, 6, 5, 3, 5, 8, 7, 7, 7, 6, 8, 10, 8, 9, 8, 7, 8, 4, 7, 12, 6, 8, 7, 12, 11, 6, 9, 7, 17, 9, 9

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

a(35) >= 9. See link to factordb.com - Hugo Pfoertner, Aug 07 2019

LINKS

EXAMPLE

If p=29 then (29^29 + 1) contains 7 distinct prime factors.

MATHEMATICA

f[n_] := Length@ FactorInteger[Prime[n]^Prime[n] + 1]; Array[f, 20] (* Robert G. Wilson v, Apr 06 2006 *)

PROG

(PARI) { for(n=1, 20, p = prime(n); d = factor(p^p+1); dec=matsize(d); print1(dec[1], ", "); ); } \\ R. J. Mathar, Mar 29 2006

CROSSREFS

KEYWORD

nonn,more,hard

AUTHOR

EXTENSIONS

8 more terms from R. J. Mathar, Mar 29 2006

a(19)-a(25) from Robert G. Wilson v, Apr 06 2006

a(26)-a(32) from Sean A. Irvine, Oct 20 2011

a(33)-a(34) from Hugo Pfoertner, Aug 07 2019

a(28) corrected by Sean A. Irvine, Aug 04 2023

STATUS

approved