A008329 Number of divisors of p+1, p prime.

2, 3, 4, 4, 6, 4, 6, 6, 8, 8, 6, 4, 8, 6, 10, 8, 12, 4, 6, 12, 4, 10, 12, 12, 6, 8, 8, 12, 8, 8, 8, 12, 8, 12, 12, 8, 4, 6, 16, 8, 18, 8, 14, 4, 12, 12, 6, 12, 12, 8, 12, 20, 6, 18, 8, 16, 16, 10, 4, 8, 6, 12, 12, 16, 4, 8, 6, 6, 12, 12, 8, 24, 10, 8, 12, 16, 16, 4, 8, 8, 24, 4, 20, 8, 16

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A000005, A008864.

Programs

Magma

[NumberOfDivisors(NthPrime(n)+1): n in [1..100]]; // Vincenzo Librandi, Mar 25 2018

Maple

for i from 1 to 500 do if isprime(i) then print(tau(i+1)); fi; od;
A008329 := proc(n)
        numtheory[tau](ithprime(n)+1) ;
end proc: # R. J. Mathar, Oct 30 2015

Mathematica

DivisorSigma[0,#]&/@(Prime[Range[100]]+1)  (* Harvey P. Dale, Apr 12 2011 *)

PARI

a(n) = numdiv(prime(n)+1); \\ Michel Marcus, Mar 25 2018

Formula

a(n) = A000005(A008864(n)). - Sean A. Irvine, Mar 25 2018

Extensions

Offset corrected by Leroy Quet, Oct 08 2008