A001772 - OEIS

A001772

Numbers k such that 11*2^k - 1 is prime.
(Formerly M2145 N0854)

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