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a(2)=1; for n>2, a(n) = A109742(n)/3.
1

%I #7 Aug 03 2021 19:01:31

%S 1,3,9,41,231,1551,12037,105861,1039539,11268059,133585089,1718984673,

%T 23857531519,355190381031,5646040979901,95432906354621,

%U 1709068974897867,32325104169244851,643869687410800249,13471540400560532889,295384662114697463319

%N a(2)=1; for n>2, a(n) = A109742(n)/3.

%Y Cf. A000166, A109742.

%K nonn

%O 2,2

%A _N. J. A. Sloane_, Aug 13 2005