A129493 Composite numbers k such that 3^k mod k is a power of 3.

6, 10, 12, 14, 18, 22, 24, 26, 30, 33, 34, 36, 38, 39, 46, 51, 54, 56, 57, 58, 62, 63, 66, 69, 72, 74, 78, 82, 86, 87, 90, 91, 92, 93, 94, 99, 104, 106, 108, 111, 112, 116, 117, 118, 120, 121, 122, 123, 124, 129, 132, 134, 135, 141, 142, 144, 146, 148, 154, 158, 159

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

Cf. A036236, A122780, A129492, A129494, A129495, A129496, A129497.

Sequence in context: A336323 A175352 A175397 * A036350 A295076 A088829

Adjacent sequences: A129490 A129491 A129492 * A129494 A129495 A129496

Keyword

easy,nonn

Author

Robert G. Wilson v, Apr 17 2007

Status

approved