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A200823 Numbers n such that (2^n + n)*2^n + 1 is prime. 7
1, 3, 6, 14, 21, 27, 51, 61, 103, 123, 126, 414, 499, 1509, 2389 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The generalization of this sequence is possible with the primes of the form  (b^n +-k)*b^n +-1.

LINKS

Table of n, a(n) for n=1..15.

Henri Lifchitz, New forms of primes

EXAMPLE

3 is in the sequence because (2^3 + 3)*2^3 + 1 = 89 is prime.

MATHEMATICA

lst={}; Do[If[PrimeQ[(2^n + n)*2^n+1], AppendTo[lst, n]], {n, 5000}]; lst

PROG

(PARI) is(n)=ispseudoprime((2^n+n)<<n+1) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A200816, A200817, A200818, A200819, A200821, A200822, A200832.

Sequence in context: A109757 A075189 A291987 * A093866 A056596 A026341

Adjacent sequences:  A200820 A200821 A200822 * A200824 A200825 A200826

KEYWORD

nonn

AUTHOR

Michel Lagneau, Nov 23 2011

STATUS

approved

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Last modified January 27 15:14 EST 2020. Contains 331295 sequences. (Running on oeis4.)