

A268061


Numbers n such that 7*8^n  1 is prime.


4




OFFSET

1,1


COMMENTS

a(10) > 2*10^5.
Terms are A001771(n)/3 that are integers.


REFERENCES

R. K. Guy, Unsolved Problems in Theory of Numbers, Section A3.


LINKS

Table of n, a(n) for n=1..9.
H. C. Williams, The primality of certain integers of the form 2Ar^n  1, Acta Arith. 39 (1981), 717.


MATHEMATICA

Select[Range[0, 200000], PrimeQ[7*8^#  1] &]


PROG

(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(7*8^n1), print1(n, ", "))) \\ Altug Alkan, Jan 25 2016


CROSSREFS

Cf. similar sequences of the form k*(k+1)^n1: A003307 (k=2), ... (k=3), A046865 (k=4), A079906 (k=5), A046866 (k=6), this sequence (k=7), ... (k=8), A056725 (k=9), A046867 (k=10), A079907 (k=11).
Cf. A001771, A002235, A005541, A247260.
Sequence in context: A146448 A192169 A290470 * A298358 A023370 A181071
Adjacent sequences: A268058 A268059 A268060 * A268062 A268063 A268064


KEYWORD

nonn,hard,more


AUTHOR

Robert Price, Jan 25 2016


STATUS

approved



