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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.)