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A139463
Numbers n such that (product of the first n odd primes) - 2*prime(n+2) is a prime.
3
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
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
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