A046809 a(n) is the least integer greater than a(n-1) such that a(n-1)*2^a(n) - 1 is prime, a(1) = 1.

1, 2, 4, 5, 8, 10, 11, 26, 286, 365, 602, 630, 713, 808, 1327, 3561, 3566, 5286, 5477, 10600, 13485, 15441, 17339, 76856, 277718, 279098, 977278, 3437687, 3564664, 3883403, 4254462, 4972164

Offset

1,2

Comments

Previous name was: Recursive sequence of indices of Proth primes a*2^b - 1.

Links

Table of n, a(n) for n=1..32.

Chris K. Caldwell, The Prime Pages, 488639*2^3437688-1 (977278*2^3437687-1)

Chris K. Caldwell, The Prime Pages, 3437687*2^3564664-1

Chris K. Caldwell, The Prime Pages, 445583*2^3883406-1 (3564664*2^3883403-1)

Chris K. Caldwell, The Prime Pages, 3883403*2^4254462-1

Chris K. Caldwell, The Prime Pages, 2127231*2^4972165-1 (4254462*2^4972164-1)

Y. Gallot, Proth.exe: Windows Program for Finding Large Primes

Prog

(PARI) a=1; until(, print1(a, ", "); for(b=a+1, +oo, if(ispseudoprime(a*2^b-1), a=b; break()))) \\ Jeppe Stig Nielsen, Apr 29 2022

Crossrefs

Cf. A046808.

Sequence in context: A067938 A306073 A018457 * A112777 A392291 A188972

Adjacent sequences: A046806 A046807 A046808 * A046810 A046811 A046812

Keyword

hard,nonn,more

Author

Chad Davis (cad16(AT)po.cwru.edu)

Extensions

a(25)-a(27) from Kellen Shenton Apr 29 2022

a(28)-a(32) from Kellen Shenton, Jun 15 2025

Status

approved