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A050897
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Numbers k such that 277*2^k-1 is prime.
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0
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5, 21, 101, 105, 333, 461, 933, 1041, 2157, 3321, 5177, 5513, 5781, 9737, 11505, 16457, 17357, 490805
(list;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..18.
Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300
Wilfrid Keller, List of primes k.2^n - 1 for k < 300
Kosmaj, Riesel list k<300.
Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime
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PROG
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(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
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CROSSREFS
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Sequence in context: A201869 A017968 A017969 * A338673 A199215 A204061
Adjacent sequences: A050894 A050895 A050896 * A050898 A050899 A050900
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KEYWORD
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hard,nonn
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AUTHOR
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N. J. A. Sloane, Dec 29 1999
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EXTENSIONS
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490805 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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STATUS
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approved
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