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
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