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A201357 Numbers k such that (2^k + k + 1)*2^k - 1 is prime. 7
1, 13, 1468, 2701, 2959, 3735, 8686, 11920 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
13 is in the sequence because (2^13 + 13 + 1)*2^13 - 1 = 67223551 is prime.
MATHEMATICA
lst={}; Do[If[PrimeQ[(2^n + n+1)*2^n-1], AppendTo[lst, n]], {n, 10000}]; lst
PROG
(PARI) is(n)=isprime((2^n+n+1)<<n-1) \\ Charles R Greathouse IV, Feb 17 2017
(Python)
from sympy import isprime
def afind(limit, startk=1):
pow2 = 2**startk
for k in range(startk, limit+1):
if isprime((pow2 + k + 1)*pow2 - 1):
print(k, end=", ")
pow2 *= 2
afind(1500) # Michael S. Branicky, Jan 12 2022
CROSSREFS
Sequence in context: A353030 A064962 A242562 * A220551 A185073 A185193
KEYWORD
nonn,hard,more
AUTHOR
Michel Lagneau, Nov 30 2011
EXTENSIONS
a(8) from Michael S. Branicky, Jan 12 2022
STATUS
approved

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Last modified July 23 21:46 EDT 2024. Contains 374575 sequences. (Running on oeis4.)