A182156 Numbers k such that 2^k-61 is prime.

6, 7, 11, 15, 17, 21, 23, 25, 31, 35, 57, 67, 85, 165, 213, 217, 331, 351, 695, 721, 815, 825, 1007, 1403, 1725, 1833, 3213, 4897, 5657, 6575, 7345, 7473, 9633, 10075, 12727, 15131, 15931, 17627, 19687, 29687, 34621, 39387, 49813

Offset

1,1

Comments

For these k, N=2^(k-1)*(2^k-61) is of abundance A033880(N)=60.

The five smallest numbers of abundance 60 are 96, 126, 4288, 2034688, 535871488. Four out of these five are of the form 2^(k-1)*(2^k-61).

Links

Table of n, a(n) for n=1..43.

Prog

(PARI) for(k=1, 999, ispseudoprime(2^k-61)&print1(k", "))

Crossrefs

Cf. A033880.

Sequence in context: A270431 A315832 A224856 * A166496 A267413 A297254

Adjacent sequences: A182153 A182154 A182155 * A182157 A182158 A182159

Keyword

nonn,more

Author

M. F. Hasler, Apr 14 2012

Extensions

a(27)-a(39) from Michael S. Branicky, Aug 14 2021

a(40)-a(43) from Michael S. Branicky, Apr 03 2023

Status

approved