%I #7 Dec 12 2021 20:13:10
%S 3,9,18,18,9,9,36,9,27,27,9,9,9,9,9,27,9,63,9,9,9,9,27,18,36,9,9,18,
%T 18,18,9,9,9,9,4941,9,9,9,9,9,9,9,9,9,144,18,9,153,333,63,18,9,27,9,9,
%U 9,9,9,9,9,9,9,9,9,9,9,9,18,18,9,9,18,18,18,9,9,9,9,9,9,9,9,9,81,9,9,9,9,54
%N GCD of reverse(3^n) and reverse(3^(n+1)).
%F a(n) = GCD(A004167(n), A004167(n+1)).
%e These common divisors are always divisible by 3.
%t rd[x_] :=FromDigits[Reverse[IntegerDigits[x]]] Table[GCD[rd[3^w], rd[3^(w+1)]], {w, 1, 100}]
%Y Cf. A004167.
%K base,nonn
%O 1,1
%A _Labos Elemer_, Jan 25 2005