|
%I #23 Sep 20 2020 01:23:25
%S 19,75,99,135,163,175,219,249,367,607,651,1005,1355,1487,2341,5509,
%T 8667,9995,10987,13671,17235,24613,25087,25671,27655,35611,37879,
%U 41755,47163,57423
%N Numbers k such that N*2^k + 1 is prime where N = 9999999999999999999999988888888888888888887777777777777777766666666666665555555555544444443333322211.
%C 9999999999999999999999988888888888888888887777777777777777766666666666665555555555544444443333322211 is a 100-digit prime that is easy to remember: 23 9s then 19 8s then 17 7s then 13 6s then 11 5s then 7 4s then 5 3s then 3 2s and 2 1s. Writing p(k) for prime(k), this is p(9)9 p(8)8 p(7)7 p(6)6 p(5)5 p(4)4 p(3)3 p(2)2 p(1)1.
%C a(21) > 15200. - _Jinyuan Wang_, Mar 19 2020
%C Also numbers k such that (10^100-(10^77+10^58+10^41+10^28+10^17+10^10+10^5-7)/9-12) * 2^k + 1 is prime. - _David A. Corneth_, Aug 30 2020
%Y Cf. A098466.
%K nonn,more
%O 1,1
%A _Pierre CAMI_, Sep 09 2004
%E a(18)-a(20) from _Jinyuan Wang_, Mar 19 2020
%E a(2) corrected by _Daniel Suteu_, Mar 20 2020
%E a(21)-a(30) from _Daniel Suteu_, Sep 08 2020
|
