OFFSET
1,1
COMMENTS
Complement to composite numbers: 9, 15, 21, 25, 27, 28, 35, 42, 44, 45, 48, 49, 50, 52, 55, 60, 65, 68, 70, 75, ....
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
14 is a member of the sequence since 3^14 mod 14 = 9.
MAPLE
filter:= proc(n) local k;
if isprime(n) then return false fi;
k:= 3 &^ n mod n;
k > 1 and k = 3^padic:-ordp(k, 3)
end proc:
select(filter, [$4..1000]); # Robert Israel, Dec 03 2019
MATHEMATICA
Select[Range@ 161, IntegerQ@ Log[3, PowerMod[3, #, # ]] &]
PROG
(Magma) [k:k in [2..160]| not IsPrime(k) and not IsZero(a) and (PrimeDivisors(a) eq [3]) where a is 3^k mod k ]; // Marius A. Burtea, Dec 04 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Apr 17 2007
STATUS
approved