A296031 Numbers k such that 2^(k-1) - k is prime.

5, 11, 15, 17, 27, 51, 57, 71, 117, 2073, 6251, 13671, 14217, 14627, 396128

Offset

1,1

Comments

a(15) > 200000. - Giovanni Resta, May 13 2018

Links

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

Formula

a(n) = A099439(n) + 1 = A063791(n) + 2.

Example

5 is in the sequence, because 2^4 - 5 = 11 is prime.

Mathematica

Select[Range[6500], PrimeQ[2^(# - 1) - #] &] (* Michael De Vlieger, Apr 21 2018 *)

Prog

(PARI) forstep(n=1, 10^6, 2, if(ispseudoprime(2^(n-1)-n), print1(n, ", "))); \\ Joerg Arndt, Apr 15 2018

Crossrefs

Cf. A063791, A099439.

Sequence in context: A137003 A314003 A314004 * A344214 A314005 A164355

Adjacent sequences: A296028 A296029 A296030 * A296032 A296033 A296034

Keyword

nonn,more

Author

Thomas Gajdek, Dec 03 2017

Extensions

Edited by Joerg Arndt, Apr 15 2018

a(15) from Michael S. Branicky, Apr 20 2025 using A099439

Status

approved