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A272475 Numbers n such that 2^n-1 and 3^n-1 are not coprime. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A167146 A020891 A090967 * A184016 A075254 A284913

Adjacent sequences:  A272472 A272473 A272474 * A272476 A272477 A272478

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, May 01 2016

STATUS

approved

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Last modified September 17 22:53 EDT 2019. Contains 327147 sequences. (Running on oeis4.)