A008335 - OEIS

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A008335

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

3

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

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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