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A102351
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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.
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1
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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; internal format)
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OFFSET
| 1,6
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COMMENTS
| Number of prime prime residues of the n-th prime.
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LINKS
| Carlos Rivera, Prime Puzzle 301
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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).
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MATHEMATICA
| f[n_] := Length[ Select[ Mod[ Prime[n], Prime[ Range[n]]], PrimeQ[ # ] &]]; Table[ f[n], {n, 87}] (from Robert G. Wilson v Feb 22 2005)
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CROSSREFS
| Cf. A102854.
Sequence in context: A026263 A080098 A083060 * A078173 A129759 A137467
Adjacent sequences: A102348 A102349 A102350 * A102352 A102353 A102354
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KEYWORD
| nonn
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AUTHOR
| Ray G. Opao (1260(AT)email.com), Feb 21 2005
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 22 2005
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