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A102351 Let p = prime(n); then a(n) = number of residues p mod q which are prime, as q runs through the primes less than p. 1
0, 0, 1, 1, 1, 2, 3, 2, 3, 3, 3, 4, 4, 3, 5, 4, 5, 3, 3, 5, 6, 6, 4, 7, 6, 5, 6, 6, 6, 8, 6, 7, 9, 6, 8, 6, 8, 9, 6, 7, 8, 9, 8, 10, 10, 7, 8, 8, 7, 9, 11, 11, 11, 10, 10, 9, 10, 10, 13, 11, 11, 12, 11, 12, 12, 11, 9, 11, 11, 10, 12, 15, 13, 14, 13, 13, 12, 12, 16, 14, 14, 12, 14, 14, 15, 14, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

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

LINKS

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

Carlos Rivera, Prime Puzzle 301

EXAMPLE

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).

MATHEMATICA

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

CROSSREFS

Cf. A102854.

Sequence in context: A080098 A083060 A272979 * A078173 A248005 A129759

Adjacent sequences:  A102348 A102349 A102350 * A102352 A102353 A102354

KEYWORD

nonn

AUTHOR

Ray G. Opao, Feb 21 2005

EXTENSIONS

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

STATUS

approved

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Last modified March 25 08:15 EDT 2019. Contains 321469 sequences. (Running on oeis4.)