Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #34 Jan 05 2025 19:51:38
%S 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,
%T 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,
%U 1,1,5,1,1,1,5,1,1,1,5,1,1,1,5,1,1,1,5
%N a(n) = gcd(3^n-2,2^n-3).
%C 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
%H Antti Karttunen, <a href="/A109768/b109768.txt">Table of n, a(n) for n = 1..10000</a>
%H Suggested by Max Alekseyev in <a href="https://web.archive.org/web/*/http://list.seqfan.eu/pipermail/seqfan/2005-August/005982.html">a Seqfan memo</a> Aug 09 2005.
%H Anatoly S. Izotov, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Papers1/43-2/paper43-2-6.pdf">On prime divisors of GCD(3^n-2,2^n-3)</a>, Fibonacci Quarterly 43, May 2005, pp. 130-131.
%t Table[GCD[3^n - 2, 2^n - 3], {n, 120}] (* _Michael De Vlieger_, Mar 10 2016 *)
%o (PARI) a(n) = gcd(3^n-2, 2^n-3); \\ _Michel Marcus_, Mar 10 2016
%Y Cf. A196627, A196628.
%K nonn
%O 1,3
%A _John W. Layman_, Aug 13 2005