A008335 Number of distinct primes dividing p+1 as p runs through the primes.

1, 1, 2, 1, 2, 2, 2, 2, 2, 3, 1, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 3, 2, 3, 2, 2, 3, 3, 1, 3, 3, 3, 3, 2, 2, 2, 3, 3, 3, 3, 2, 2, 3, 2, 2, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 2, 2, 3, 2, 3, 3, 3, 2, 3, 2, 2, 3, 3, 3, 3, 2, 3, 3, 2, 4, 2, 3, 3, 4, 2, 2, 3, 3, 3, 3, 2, 4, 2, 3, 3, 2, 3, 2

Offset

1,3

Links

T. D. Noe, Table of n, a(n) for n=1..10000

Formula

a(n) = A001221(A008864(n)). - Michel Marcus, Mar 29 2016

Maple

for i from 1 to 500 do if isprime(i) then print(nops(factorset(i+1))); fi; od;

Mathematica

a[n_] := PrimeNu[Prime[n]+1]; Array[a, 100] (* Amiram Eldar, Sep 10 2024 *)

Prog

(PARI) a(n) = omega(prime(n)+1); \\ Michel Marcus, Mar 29 2016

Crossrefs

Cf. A001221, A008864, A023514.

Sequence in context: A068212 A323015 A105194 * A106031 A055175 A339930

Adjacent sequences: A008332 A008333 A008334 * A008336 A008337 A008338

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved