OFFSET
1,4
COMMENTS
REFERENCES
Zhi-Wei Sun, Problems on combinatorial properties of primes, in: M. Kaneko, S. Kanemitsu and J. Liu (eds.), Number Theory: Plowing and Starring through High Wave Forms, Proc. 7th China-Japan Seminar (Fukuoka, Oct. 28 - Nov. 1, 2013), Ser. Number Theory Appl., Vol. 11, World Sci., Singapore, 2015, pp. 169-187.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..100
Zhi-Wei Sun, Problems on combinatorial properties of primes, arXiv:1402.6641 [math.NT], 2014.
EXAMPLE
a(5) = 4 since prime(4*5)^2-2 = 71^2-2 = 5039 = prime(135*5).
MATHEMATICA
P[n_, p_]:=PrimeQ[p]&&Mod[PrimePi[p], n]==0
Do[k=0; Label[bb]; k=k+1; If[P[n, Prime[k*n]^2-2], Goto[aa]]; Goto[bb]; Label[aa]; Print[n, " ", k]; Continue, {n, 1, 60}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Jul 17 2015
STATUS
approved