A387925 Integers k such that 511*2^k - 1 is prime.

1, 7, 9, 11, 15, 23, 31, 67, 103, 105, 113, 121, 127, 149, 231, 357, 471, 573, 627, 765, 1135, 1595, 2057, 2099, 3329, 5557, 6087, 10565, 13603, 14287, 14931, 15131, 16591, 17261, 18141, 25925, 27257, 33261, 35123, 37737, 53677, 54373, 58561, 79405, 107065, 111899

Offset

1,2

Comments

All terms must be odd, since 3 divides 511*2^k - 1 for k even. - Michael S. Branicky, Sep 16 2025

Links

Table of n, a(n) for n=1..46.

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Mathematica

Select[Range[1000], PrimeQ[511*2^# - 1] &] (* Amiram Eldar, Sep 13 2025 *)

Crossrefs

Cf. A387926, A387927.

Cf. A000043, A002235, A001771, A002237, A050541, A050557, A050589, A050886.

Sequence in context: A254937 A222947 A107226 * A252663 A393805 A317633

Adjacent sequences: A387922 A387923 A387924 * A387926 A387927 A387928

Keyword

nonn

Author

Chris Hennick, Sep 13 2025

Extensions

a(18)-a(28) from Amiram Eldar, Sep 13 2025

a(29)-a(46) from Michael S. Branicky, Sep 14 2025

Status

approved