

A280846


Numbers k such that all four of the numbers 2^k + 2k + 1 are nonprime.


0



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
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..65.


EXAMPLE

For k=9, 2^k + 2k + 1 produces 531, 529, 495, and 493, none of which are prime.


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 *)


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
Sequence in context: A003135 A105742 A105834 * A121061 A106690 A173015
Adjacent sequences: A280843 A280844 A280845 * A280847 A280848 A280849


KEYWORD

nonn


AUTHOR

Maverick K. Morrison, Jan 15 2017


STATUS

approved



