

A273870


Numbers n such that 4^(n1) == 1 (mod (n1)^2+1).


2



1, 3, 5, 17, 217, 257, 387, 8209, 20137, 37025, 59141, 65537, 283801, 649801, 1382401
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OFFSET

1,2


COMMENTS

Also, numbers n such that (4^k)^(n1) == 1 (mod (n1)^2+1) for all k >= 0.
Contains Fermat numbers (A000215) as subsequence.
Prime terms are in A273871.


LINKS

Table of n, a(n) for n=1..15.


EXAMPLE

5 is term because 4^(51) == 1 (mod (51)^2+1), i.e., 255 == 0 (mod 17).


PROG

(MAGMA) [n: n in [1..100000]  (4^(n1)1) mod ((n1)^2+1) eq 0]
(PARI) isok(n) = Mod(4, (n1)^2+1)^(n1) == 1; \\ Michel Marcus, Jun 02 2016


CROSSREFS

Cf. A000215, A019434, A273871.
Sequence in context: A171271 A056826 A278138 * A272060 A058910 A023394
Adjacent sequences: A273867 A273868 A273869 * A273871 A273872 A273873


KEYWORD

nonn,more


AUTHOR

Jaroslav Krizek, Jun 01 2016


EXTENSIONS

a(14)a(15) from Michel Marcus, Jun 02 2016
Edited by Max Alekseyev, Apr 30 2018


STATUS

approved



