A023568 Number of distinct prime divisors of prime(n)-3.

0, 0, 1, 1, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 1, 2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 3, 2, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 2, 2, 3, 2, 3, 3, 2, 3, 2, 2, 2, 3, 2, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 3, 3, 3

Offset

1,6

Comments

a(n) = 1 if prime(n) is in A057733. - Robert Israel, Dec 28 2015

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

0, 0, seq(nops(numtheory:-factorset(ithprime(i)-3)), i=3..100); # Robert Israel, Dec 28 2015

Mathematica

Join[{0, 0}, PrimeNu/@(Prime[Range[3, 100]]-3)] (* Harvey P. Dale, Sep 09 2017 *)

Crossrefs

Cf. A023569, A057733.

Sequence in context: A332992 A337788 A346510 * A081753 A332999 A334144

Adjacent sequences: A023565 A023566 A023567 * A023569 A023570 A023571

Keyword

nonn

Author

Clark Kimberling

Status

approved