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A182156
Numbers k such that 2^k-61 is prime.
0
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, 61401, 69575, 76497, 117301
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).
PROG
(PARI) for(k=1, 999, ispseudoprime(2^k-61)&print1(k", "))
CROSSREFS
Cf. A033880.
Sequence in context: A270431 A315832 A224856 * A166496 A267413 A297254
KEYWORD
nonn
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
a(44)-a(47) from Michael S. Branicky, Sep 25 2024
STATUS
approved