

A066507


Numbers k such that there is a solution to x^2 == 2^k (mod k).


1



1, 2, 4, 6, 7, 8, 10, 12, 14, 16, 17, 18, 20, 22, 23, 24, 26, 28, 30, 31, 32, 34, 36, 38, 40, 41, 42, 44, 46, 47, 48, 49, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 71, 72, 73, 74, 76, 78, 79, 80, 82, 84, 86, 88, 89, 90, 92, 94, 96, 97, 98, 100, 102, 103, 104, 106, 108, 110
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

All even numbers are in this sequence.
Odd terms in the sequence are numbers whose prime factors are +1 (mod 8) (A058529), i.e., odd k such that x^2 == 2 (mod k) has a solution.  Jason Earls, Jan 22 2002


LINKS

Table of n, a(n) for n=1..69.


PROG

(PARI) isok(n) = {for (x=0, n1, if (Mod(x, n)^2 == Mod(2, n)^n, return (1)); ); return (0); } \\ Michel Marcus, Nov 20 2013


CROSSREFS

Cf. A058529, A001132, A057126.
Sequence in context: A153282 A014661 A047511 * A285140 A015932 A030493
Adjacent sequences: A066504 A066505 A066506 * A066508 A066509 A066510


KEYWORD

nonn


AUTHOR

Benoit Cloitre, Jan 04 2002


EXTENSIONS

Corrected by Vladeta Jovovic, Jan 22 2002
More terms from Jason Earls, Jan 22 2002


STATUS

approved



