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%I #21 Apr 27 2021 02:15:06
%S 3,8,23,77,281,1073,4193,16577,65921,262913,1050113,4197377,16783361,
%T 67121153,268460033,1073790977,4295065601,17180065793,68719869953,
%U 274878693377,1099513200641,4398049656833,17592192335873,70368756760577,281475001876481,1125899957174273,4503599728033793
%N a(0)=3; for n > 0, a(n) = 2^(2*n) + 3*2^(n-1) + 1.
%C A bisection of A257418. Apart from first term, same as A036562.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-14,8).
%F From _Chai Wah Wu_, Apr 26 2021: (Start)
%F a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n > 3.
%F G.f.: -(4*x - 3)*(x^2 + 3*x - 1)/((x - 1)*(2*x - 1)*(4*x - 1)). (End)
%Y Cf. A257418, A036562, A343175.
%K nonn,easy
%O 0,1
%A _N. J. A. Sloane_, Apr 26 2021
%E a(17)-a(26) from _Martin Ehrenstein_, Apr 26 2021
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