OFFSET
1,1
COMMENTS
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.
a(21) > 15200. - Jinyuan Wang, Mar 19 2020
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
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Sep 09 2004
EXTENSIONS
a(18)-a(20) from Jinyuan Wang, Mar 19 2020
a(2) corrected by Daniel Suteu, Mar 20 2020
a(21)-a(30) from Daniel Suteu, Sep 08 2020
a(31)-a(34) from Michael S. Branicky, Jun 28 2024
STATUS
approved