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A139461 Numbers k such that 2*prime(k+2) + product (first k odd primes) is prime, i.e., k such that primorial(k+1)/2 + 2*prime(k+2) is prime. 3
1, 2, 3, 4, 8, 9, 11, 12, 27, 28, 37, 47, 64, 321, 415, 1222, 1649, 2937, 3600, 6149, 12481 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(22) > 25000. - Robert Price, Aug 06 2017

LINKS

Table of n, a(n) for n=1..21.

MATHEMATICA

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

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, A139462, A139463.

Sequence in context: A002971 A157318 A158031 * A126421 A116111 A253278

Adjacent sequences:  A139458 A139459 A139460 * A139462 A139463 A139464

KEYWORD

nonn

AUTHOR

Artur Jasinski, Apr 22 2008

EXTENSIONS

a(16)-a(21) from Robert Price, Aug 06 2017

STATUS

approved

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Last modified November 13 12:45 EST 2019. Contains 329094 sequences. (Running on oeis4.)