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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 Table of n, a(n) for n=1..24. Wilfrid Keller, List of primes k.2^n - 1 for k < 300 Kosmaj, Riesel list k<300. 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. Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime 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 Adjacent sequences: A001769 A001770 A001771 * A001773 A001774 A001775 KEYWORD hard,nonn,nice,more AUTHOR N. J. A. Sloane 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.)