A301744 Numbers k such that 2^k - 2*k + 1 is prime.

0, 3, 5, 6, 8, 11, 12, 13, 18, 25, 31, 35, 114, 152, 186, 228, 245, 308, 360, 371, 575, 685, 721, 732, 1361, 2394, 3138, 3446, 5964, 9482, 22793, 51233, 112800, 120491, 199615, 416641

Offset

1,2

Comments

Terms through 1361 correspond to provable primes; terms beyond 1361 correspond to probable primes.

After 22793, there are no more terms through 40000. - Jon E. Schoenfield, Mar 27 2018

a(37) > 5*10^5. - Robert Price, Jun 01 2018

Links

Table of n, a(n) for n=1..36.

Maple

select(k->isprime(2^k-2*k+1), [$0..3000]); # Muniru A Asiru, Apr 03 2018

Mathematica

Select[Range[0, 1000], PrimeQ[2^# - 2*# + 1] &]

Prog

(Magma) [n: n in [0..1000] |IsPrime(2^n-2*n+1)]; // Vincenzo Librandi, Mar 27 2018
(PARI) isok(n) = isprime(2^n-2*n+1); \\ Michel Marcus, Mar 27 2018

Crossrefs

Cf. A100359, A100361, A301634.

Sequence in context: A268896 A014254 A131422 * A087720 A309544 A154111

Adjacent sequences: A301741 A301742 A301743 * A301745 A301746 A301747

Keyword

nonn,more,hard

Author

Vaclav Kotesovec, Mar 26 2018

Extensions

a(31) from Jon E. Schoenfield, Mar 27 2018

a(32)-a(34) from Robert Price, Apr 03 2018

a(35)-a(36) from Robert Price, Jun 01 2018

Status

approved