

A002255


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


22



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
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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. 381384.
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, 697712. [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), 673681.
Index entries for sequences of n such that k*2^n1 (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: A101956 A273064 A002238 * A272649 A266813 A192116
Adjacent sequences: A002252 A002253 A002254 * A002256 A002257 A002258


KEYWORD

hard,nonn


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Added more terms (from A032353), Joerg Arndt, Apr 07 2013


STATUS

approved



