OFFSET
1,2
COMMENTS
Includes 341 which is first pseudoprime to base 2 and distinguishes sequence from A008578.
First composite even term is a(14868) = 161038 = A006935(2). - Max Alekseyev, Feb 11 2015
If k is a term, then so is 2^k - 1. - Max Alekseyev, Sep 22 2016
Terms of the form 2^k - 2 correspond to k in A296104. - Max Alekseyev, Dec 04 2017
If 2^k - 1 is a term, then so is k. - Thomas Ordowski, Apr 27 2018
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..20000
FORMULA
Equals {1} U A000040 U A001567 U A006935 = A001567 U A006935 U A008578. - Ray Chandler, Dec 07 2003; corrected by Max Alekseyev, Feb 11 2015
MATHEMATICA
Prepend[ Select[ Range@370, PowerMod[2, #, #] == 2 &], {1, 2}] // Flatten (* Robert G. Wilson v, May 16 2018 *)
PROG
(PARI) is(n)=Mod(2, n)^n==2 \\ Charles R Greathouse IV, Mar 11 2014
(Python)
def ok(n): return pow(2, n, n) == 2%n
print([k for k in range(1, 400) if ok(k)]) # Michael S. Branicky, Jun 03 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved