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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
OFFSET
1,2
COMMENTS
a(22) > 25000. - Robert Price, Aug 06 2017
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 *)
KEYWORD
nonn
AUTHOR
Artur Jasinski, Apr 22 2008
EXTENSIONS
a(16)-a(21) from Robert Price, Aug 06 2017
STATUS
approved