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GCD of reverse(3^n) and reverse(3^(n+1)).
0

%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