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A115973
Number of distinct prime factors of p^p + 1 where p is prime(n).
2
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
OFFSET
1,2
COMMENTS
a(35) >= 9. See link to factordb.com - Hugo Pfoertner, Aug 07 2019
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
Cf. A125137.
Sequence in context: A266286 A045892 A160791 * A057047 A361168 A101447
KEYWORD
nonn,more,hard
AUTHOR
Parthasarathy Nambi, Mar 14 2006
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