A139463 Numbers n such that (product of the first n odd primes) - 2*prime(n+2) is a prime.

3, 4, 6, 10, 15, 42, 49, 56, 63, 106, 170, 182, 246, 255, 507, 627, 848, 864, 961, 1302, 3209, 4994, 7665, 7671, 16405

Offset: 1

Author

Artur Jasinski, Apr 22 2008

Keywords

• nonn
• more

Comments

a(26) > 25000. - Robert Price, Sep 27 2017

Examples

			3 is in the sequence because 3*5*7 - 2*11 = 83 is a prime.
		

Crossrefs

Cf. A067026, A067027, A139439, A139440, A139441, A139442, A139443, A139444, A139445, A139446, A139447, A139448, A139449, A139450, A139451, A139452, A139453, A139454, A139455, A139456, A139457, A103514, A139460, A139461, A139462.

Programs

Mathematica

k = 1; a = {}; Do[k = k*Prime[n]; If[PrimeQ[k - 2*Prime[n + 1]], AppendTo[a, n - 1]], {n, 2, 2000}]; a

PARI

isok(n) = isprime(prod(k=2, n+1, prime(k)) - 2*prime(n+2)); \\ Michel Marcus, Sep 27 2017

Extensions

Edited by Jens Kruse Andersen, May 03 2008

a(15)-a(25) from Robert Price, Sep 27 2017