A160129 a(n) = least prime p such that both p-+6*n are prime.

11, 17, 23, 29, 37, 43, 47, 53, 59, 67, 71, 79, 89, 89, 101, 101, 109, 131, 127, 131, 131, 137, 179, 149, 157, 193, 191, 179, 179, 193, 193, 197, 211, 227, 223, 223, 227, 233, 257, 251, 257, 257, 263, 277, 277, 281, 311, 311, 307, 307, 311, 331, 359, 337, 347

Offset

1,1

Comments

Sequence is not monotonic. For instance, a(17) = 109, a(18) = 131, a(19) = 127.

Links

Zak Seidov, Table of n, a(n) for n = 1..10000

Zak Seidov, Table of a(n) for n=10001..20000

Formula

11 and 11-+1*6 are prime, 17 and 17-+2*6 are prime, 23 and 23-+3*6 are prime.

Mathematica

lp[n_]:=Module[{p=NextPrime[6n]}, While[Total[Boole[PrimeQ[p+6{n, -n}]]] != 2, p = NextPrime[p]]; p]; Array[lp, 60] (* Harvey P. Dale, Mar 02 2023 *)

Prog

(PARI) a(n) = {p = nextprime(6*n); while (!isprime(p+6*n) || !isprime(p-6*n), p = nextprime(p+1)); p; } \\ Michel Marcus, Oct 15 2013

Crossrefs

Sequence in context: A209624 A243153 A280326 * A275682 A265402 A145481

Adjacent sequences: A160126 A160127 A160128 * A160130 A160131 A160132

Keyword

nonn

Author

Zak Seidov, May 02 2009

Extensions

Comment simplified by Michel Marcus, Oct 15 2013

Status

approved