A109768 - OEIS

A109768

a(n) = gcd(3^n-2,2^n-3).

1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5

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OFFSET

1,3

COMMENTS

The first time the inequality a(n) > 5 occurs for n = A196628(2) = 3783 with a(3783) = 26665 = 5*5333 = A196627(1)*A196627(2). - Max Alekseyev, Oct 04 2011

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Suggested by Max Alekseyev in a Seqfan memo Aug 09 2005.

Anatoly S. Izotov, On prime divisors of GCD(3^n-2,2^n-3), Fibonacci Quarterly 43, May 2005, pp. 130-131.

MATHEMATICA

Table[GCD[3^n - 2, 2^n - 3], {n, 120}] (* Michael De Vlieger, Mar 10 2016 *)

PROG

(PARI) a(n) = gcd(3^n-2, 2^n-3); \\ Michel Marcus, Mar 10 2016

CROSSREFS

Cf. A196627, A196628.

Sequence in context: A348505 A051008 A304042 * A069293 A347398 A333751

Adjacent sequences: A109765 A109766 A109767 * A109769 A109770 A109771

KEYWORD

nonn

AUTHOR

John W. Layman, Aug 13 2005

STATUS

approved