A002255 Numbers k such that 7*4^k + 1 is prime. (Formerly M0826 N0315)

1, 2, 3, 7, 10, 13, 25, 26, 46, 60, 87, 90, 95, 145, 160, 195, 216, 308, 415, 902, 1128, 3307, 6748, 7747, 8348, 11193, 27243, 44033, 47665, 103542, 141517, 280908, 402267, 405615, 745926, 1069956, 1083900, 1457977, 1507881, 1755887

Offset

1,2

References

H. Riesel, Prime numbers and computer methods for factorization, in 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..40.

Ray Ballinger, Proth Search Page.

C. K. Caldwell, The Prime Pages.

R. K. Guy, The strong law of small numbers. Amer. Math. Monthly 95 (1988), no. 8, 697-712. [Annotated scanned copy]

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.

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Prog

(PARI) is(n)=ispseudoprime(7*4^n+1) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

See A032353 (which is the main entry for this sequence) for more terms.

Sequence in context: A273064 A341238 A002238 * A272649 A266813 A344232

Adjacent sequences: A002252 A002253 A002254 * A002256 A002257 A002258

Keyword

hard,nonn

Author

N. J. A. Sloane

Extensions

More terms (from A032353) added by Joerg Arndt, Apr 07 2013

Status

approved