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A050897
Numbers k such that 277*2^k-1 is prime.
0
5, 21, 101, 105, 333, 461, 933, 1041, 2157, 3321, 5177, 5513, 5781, 9737, 11505, 16457, 17357, 490805
OFFSET
1,1
PROG
(PARI) is(n)=ispseudoprime(277*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017
(Python)
from sympy import isprime
def afind(limit, startat=0):
pow2 = 2**startat
for k in range(startat, limit+1):
if isprime(277*pow2-1): print(k, end=", ")
pow2 *= 2
afind(3333) # Michael S. Branicky, May 21 2021
CROSSREFS
Sequence in context: A201869 A017968 A017969 * A338673 A199215 A204061
KEYWORD
hard,nonn
AUTHOR
N. J. A. Sloane, Dec 29 1999
EXTENSIONS
490805 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
STATUS
approved