A098467 Numbers k such that N*2^k + 1 is prime where N = 9999999999999999999999988888888888888888887777777777777777766666666666665555555555544444443333322211.

19, 75, 99, 135, 163, 175, 219, 249, 367, 607, 651, 1005, 1355, 1487, 2341, 5509, 8667, 9995, 10987, 13671, 17235, 24613, 25087, 25671, 27655, 35611, 37879, 41755, 47163, 57423, 62619, 85935, 89025, 94895

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

Links

Table of n, a(n) for n=1..34.

Crossrefs

Cf. A098466.

Sequence in context: A290241 A159997 A073566 * A244631 A304513 A041698

Adjacent sequences: A098464 A098465 A098466 * A098468 A098469 A098470

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