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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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified September 24 22:14 EDT 2023. Contains 365582 sequences. (Running on oeis4.)