A272475 Numbers n such that 2^n-1 and 3^n-1 are not coprime.

4, 6, 8, 10, 11, 12, 16, 18, 20, 22, 23, 24, 28, 30, 32, 33, 35, 36, 40, 42, 43, 44, 46, 48, 50, 52, 54, 55, 56, 58, 60, 64, 66, 68, 69, 70, 72, 75, 76, 77, 78, 80, 82, 83, 84, 86, 88, 90, 92, 95, 96, 99, 100, 102, 104, 105, 106, 108, 110, 112, 114, 115, 116, 117

Offset

1,1

Comments

Complement of A263647.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

gcd(2^4-1, 3^4-1) = gcd(15,80) = 5, so a(1) = 4.

Mathematica

Select[Range[200], ! GCD[2^# - 1, 3^# - 1] == 1 &]

Prog

(Magma) [n: n in [1..200] | not Gcd(2^n-1, 3^n-1) eq 1];
(PARI) isok(n) = gcd(2^n-1, 3^n-1) != 1; \\ Michel Marcus, May 01 2016

Crossrefs

Cf. A263647.

Sequence in context: A340848 A090967 A349707 * A184016 A075254 A284913

Adjacent sequences: A272472 A272473 A272474 * A272476 A272477 A272478

Keyword

nonn

Author

Vincenzo Librandi, May 01 2016

Status

approved