A280846 Numbers k such that all four of the numbers 2^k +- 2k +- 1 are nonprime.
9, 10, 16, 17, 19, 20, 21, 22, 23, 24, 26, 29, 30, 33, 34, 36, 37, 38, 39, 40, 42, 43, 44, 45, 46, 47, 48, 49, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 82, 83, 84, 86, 87, 88, 89, 90, 91
Offset: 1
Keywords
Examples
For k=9, 2^k +- 2k +- 1 produces 531, 529, 495, and 493, none of which are prime.
Crossrefs
Cf. A061761 (numbers of the form 2^n + 2*n - 1), A105330 (numbers n such that 2^(n+1) + 2n + 1 is prime), A163115 (primes of the form 2^n + 2*n + 1), A173168 (primes of the form 2^k + 2k - 1). - Jon E. Schoenfield, Jan 22 2017
Programs
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Mathematica
Select[Range[100],NoneTrue[Flatten[{2^#+2#+{1,-1},2^#-2#+{1,-1}}],PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 24 2018 *)