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A139440 Numbers n such that primorial(n)/2 - 4 is prime. 5
3, 4, 5, 7, 12, 15, 26, 31, 50, 71, 186, 273, 366, 1542, 1929, 3687, 4407, 15395, 15433 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(20) > 25000. - Robert Price, Dec 03 2016

LINKS

Table of n, a(n) for n=1..19.

MATHEMATICA

k = 1; a = {}; Do[k = k*Prime[n]; If[PrimeQ[k - 4], Print[n]; AppendTo[a, n]], {n, 2, 366}]; a

CROSSREFS

Cf. A067026, A067027, A139439-A139457, A103514.

Sequence in context: A092859 A173444 A120424 * A102607 A079463 A190213

Adjacent sequences:  A139437 A139438 A139439 * A139441 A139442 A139443

KEYWORD

nonn

AUTHOR

Artur Jasinski, Apr 21 2008

EXTENSIONS

a(14)-a(15) from Ray Chandler, Jun 16 2013

a(16)-a(17) from Robert Price, Aug 16 2016

a(18) from Robert Price, Dec 03 2016

Added missing term, 15395 by Robert Price, Dec 28 2016

STATUS

approved

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Last modified December 16 15:00 EST 2018. Contains 318169 sequences. (Running on oeis4.)