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A100361
Numbers k such that 2^k - k + 1 is prime.
7
0, 1, 2, 4, 6, 16, 18, 54, 58, 100, 120, 504, 1302, 3234, 14748, 16102, 22782, 34656, 64764, 70866, 194940, 274074, 313344, 331416, 354640
OFFSET
1,3
COMMENTS
a(21) > 150000. - Giovanni Resta, Mar 18 2014
a(26) > 5*10^5. - Robert Price, Oct 13 2014
MAPLE
A100361:=n->`if`(isprime(2^n-n+1), n, NULL): seq(A100361(n), n=0..10^3); # Wesley Ivan Hurt, Oct 13 2014
MATHEMATICA
{ta={{0}}, tb={{0}}}; Do[g=n; s=2^n-n+1; If[PrimeQ[s], Print[n]; ta=Append[ta, n]; tb=Append[tb, s]], {n, 1, 10000}]; {ta, tb, g}
PROG
(PARI) is(n)=ispseudoprime(2^n-n+1) \\ Charles R Greathouse IV, Feb 20 2017
KEYWORD
nonn,hard,more
AUTHOR
Labos Elemer, Nov 19 2004
EXTENSIONS
a(15)-a(20) from Giovanni Resta, Mar 18 2014
a(21)-a(25) from Robert Price, Oct 13 2014
STATUS
approved