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A130771

Numbers n not divisible by 3 for which neither 2n-3 nor 2n+3 are primes.

26, 44, 59, 61, 79, 86, 103, 106, 109, 125, 128, 131, 146, 149, 151, 161, 163, 166, 169, 179, 184, 187, 194, 205, 224, 236, 239, 254, 257, 265, 266, 268, 271, 274, 278, 281, 289, 293, 296, 304, 313, 316, 326, 334, 341, 346, 350, 355, 359, 364, 367, 376, 389, 391

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OFFSET

1,1

COMMENTS

This is A130699 with the trivial multiples of 3 removed.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..2500

EXAMPLE

26 because 2*26+3=55 is not a prime, nor is 2*26-3=49.

MATHEMATICA

Select[Range[400], !Divisible[#, 3]&&NoneTrue[2#+{3, -3}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 19 2018 *)

PROG