A249420 Least number m>1 such that m*prime(n)-2 is prime.

2, 3, 3, 3, 3, 3, 5, 7, 3, 11, 9, 3, 9, 3, 3, 3, 5, 3, 3, 3, 7, 9, 11, 5, 7, 5, 3, 23, 7, 3, 3, 5, 3, 7, 5, 21, 7, 3, 3, 5, 9, 3, 3, 3, 5, 9, 3, 7, 29, 7, 5, 5, 15, 3, 3, 3, 11, 3, 3, 11, 7, 3, 3, 5, 3, 5, 3, 3, 3, 7, 11, 9, 9, 3, 15, 5, 9, 7, 3, 7, 9, 13, 3

Offset

1,1

Links

Zak Seidov, Table of n, a(n) for n = 1..1000

Formula

a(n) = (A249419(n)+2)/prime(n).

Mathematica

lnm[n_]:=Module[{m=2, p=Prime[n]}, While[!PrimeQ[m*p-2], m++]; m]; Array[ lnm, 90] (* Harvey P. Dale, Oct 22 2019 *)

Prog

(PARI) a(n) = {m = 2; pn = prime(n); while (!isprime(m*pn-2), m++); m; } \\ Michel Marcus, Oct 29 2014

Crossrefs

Sequence in context: A284725 A055767 A029110 * A103959 A035375 A354143

Adjacent sequences: A249417 A249418 A249419 * A249421 A249422 A249423

Keyword

nonn

Author

Zak Seidov, Oct 28 2014

Status

approved