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a(n)=((2*Sqrt[2] + 3)^(2^(n - 1) - 1) - (3 - 2*Sqrt[2])^(2^(n - 1) - 1))/(4*Sqrt[2]).
3

%I #2 Mar 31 2012 10:22:08

%S 0,1,35,40391,53789260175,95393218491883573553951,

%T 300027707381709879256191290532493317737977820735

%N a(n)=((2*Sqrt[2] + 3)^(2^(n - 1) - 1) - (3 - 2*Sqrt[2])^(2^(n - 1) - 1))/(4*Sqrt[2]).

%t Table[Expand[((2*Sqrt[2] + 3)^(2^(n - 1) - 1) - (3 - 2*Sqrt[2])^(2^(n - 1) - 1))/(4*Sqrt[2])], {n, 1, 10}] (*Artur Jasinski*)

%Y Cf. A001109, A139474, A139475, A139476.

%K nonn

%O 1,3

%A _Artur Jasinski_, Apr 22 2008