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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
OFFSET
1,5
LINKS
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
KEYWORD
nonn
STATUS
approved