A002263 Numbers k such that 25*4^k + 1 is prime. (Formerly M0721 N0269)

1, 2, 3, 5, 10, 11, 26, 32, 39, 92, 116, 134, 170, 224, 277, 332, 370, 374, 640, 664, 820, 1657, 1952, 1969, 2576

Offset

1,2

References

H. Riesel, "Prime numbers and computer methods for factorization", Progress in Mathematics, Vol. 57, Birkhauser, 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..25.

Ray Ballinger, Proth Search Page

R. M. Robinson, A report on primes of the form k.2^n+1 and on factors of Fermat numbers, Proc. Amer. Math. Soc., 9 (1958), 673-681.

Mathematica

Select[Range[0, 4000], PrimeQ[(25 4^# + 1)] &] (* Vincenzo Librandi, Sep 07 2012 *)

Prog

(Magma) [n: n in [0..3000] | IsPrime(25*4^n + 1)]; // Vincenzo Librandi, Sep 07 2012
(PARI) is(n)=ispseudoprime(25*4^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

For more terms see A032362.

Sequence in context: A259732 A192229 A233696 * A249991 A039022 A182402

Adjacent sequences: A002260 A002261 A002262 * A002264 A002265 A002266

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(25) from Vincenzo Librandi, Sep 07 2012

Status

approved