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A139460 a(n) = m such that 2*prime(n+m+1) + (product of n successive odd primes) is prime. 4
1, 1, 1, 1, 2, 3, 3, 1, 1, 2, 1, 1, 9, 2, 7, 21, 7, 25, 4, 3, 18, 7, 4, 7, 11, 5, 1, 1, 61, 5, 20, 6, 22, 16, 11, 17, 1, 70, 6, 5, 5, 22, 9, 52, 108, 16, 1, 32, 42, 15, 5, 66, 6, 8, 3, 38, 17, 4, 23, 93, 8, 16, 6, 1, 39, 7, 9, 10, 21, 57, 40, 2, 15, 39, 16, 7, 5, 13, 138, 95, 58, 8, 47, 11, 39 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Or, a(n) = m such that primorial(n+1)/2+2*prime(n+m+1) is prime.

For positions of 1's in this sequence see A139461

LINKS

Table of n, a(n) for n=1..85.

MATHEMATICA

k = 1; a = {}; Do[k = k*Prime[n]; m = 1; While[ ! PrimeQ[k + 2*Prime[n + m]], m++ ]; Print[m]; AppendTo[a, m], {n, 2, 200}]; 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, A139461, A139462, A139463.

Sequence in context: A171872 A005135 A290003 * A105244 A257451 A209007

Adjacent sequences:  A139457 A139458 A139459 * A139461 A139462 A139463

KEYWORD

nonn

AUTHOR

Artur Jasinski, Apr 22 2008; definition corrected May 09 2008

STATUS

approved

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Last modified November 17 08:17 EST 2018. Contains 317275 sequences. (Running on oeis4.)