1,6

Number of prime prime residues of the n-th prime.

Table of n, a(n) for n=1..87.

Carlos Rivera, Prime Puzzle 301

a(6)=2: the 6th prime is 13. 13 mod 2 = 1; 13 mod 3 = 1; 13 mod 5 = 3 (prime); 13 mod 7 = 6; 13 mod 11 = 2 (prime).

f[n_] := Length[ Select[ Mod[ Prime[n], Prime[ Range[n]]], PrimeQ[ # ] &]]; Table[ f[n], {n, 87}] (* Robert G. Wilson v, Feb 22 2005 *)

Cf. A102854.

Sequence in context: A080098 A083060 A272979 * A078173 A248005 A129759

Adjacent sequences: A102348 A102349 A102350 * A102352 A102353 A102354

nonn

Ray G. Opao, Feb 21 2005

More terms from Robert G. Wilson v, Feb 22 2005

approved