1,1

These are the primes arising in A051899.

Michael De Vlieger, Table of n, a(n) for n = 1..10000

a(29)=19 because 19 is the smallest prime p such that 2*29*p+1 is prime.

Table[k = 1; While[! PrimeQ[2 n Prime@ k + 1], k++]; Prime@ k, {n, 120}] (* Michael De Vlieger, Jul 26 2016 *)

(PARI) a(n) = p=2; while(!isprime(2*n*p+1), p = nextprime(p+1)); p; \\ Michel Marcus, Dec 10 2013

Cf. A005384, A051644-A051654, A051899.

Sequence in context: A240755 A309806 A256170 * A079294 A242789 A076733

Adjacent sequences: A051683 A051684 A051685 * A051687 A051688 A051689

nonn

Labos Elemer

approved