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A001772 Numbers k such that 11*2^k - 1 is prime.
(Formerly M2145 N0854)
3
2, 26, 50, 54, 126, 134, 246, 354, 362, 950, 1310, 2498, 6926, 11826, 31734, 67850, 74726, 96150, 374114, 696438, 743322, 1044086, 1104606, 1261478 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
REFERENCES
H. Riesel, "Prime numbers and computer methods for factorization", Progress in Mathematics, Vol. 57, Birkhäuser, Boston, 1985, Chap. 4, see pp. 381-384.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
H. C. Williams and C. R. Zarnke, A report on prime numbers of the forms M = (6a+1)*2^(2m-1)-1 and (6a-1)*2^(2m)-1, Math. Comp., 22 (1968), 420-422.
PROG
(PARI) is(n)=ispseudoprime(11*2^n-1) \\ Charles R Greathouse IV, Feb 20 2017
(Python)
from sympy import isprime
def aupto(lim): return [k for k in range(1, lim+1) if isprime(11*2**k - 1)]
print(aupto(2500)) # Michael S. Branicky, Feb 26 2021
CROSSREFS
Cf. A050525.
Cf. A002261 (11*2^k+1 is prime).
Sequence in context: A067571 A319486 A084298 * A199206 A132861 A210848
KEYWORD
hard,nonn,nice,more
AUTHOR
EXTENSIONS
More terms from Hugo Pfoertner, Jun 23 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
STATUS
approved

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Last modified July 24 07:41 EDT 2024. Contains 374575 sequences. (Running on oeis4.)