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

1,1

Comments

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

Links

Table of n, a(n) for n=1..25.

Example

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

Mathematica

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

Prog

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

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.

Sequence in context: A059618 A114736 A099417 * A287067 A310004 A214289

Adjacent sequences: A139460 A139461 A139462 * A139464 A139465 A139466

Keyword

nonn,more

Author

Artur Jasinski, Apr 22 2008

Extensions

Edited by Jens Kruse Andersen, May 03 2008

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

Status

approved