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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS 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. 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 Adjacent sequences: A050894 A050895 A050896 * A050898 A050899 A050900 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

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Last modified March 31 00:51 EDT 2023. Contains 361623 sequences. (Running on oeis4.)