A380384 - OEIS

%I #23 Feb 05 2025 22:25:42

%S 0,1,3,9,21,47,99,205,417,843,1695,3401,6813,13639,27291,54597,109209,

%T 218435,436887,873793,1747605,3495231,6990483,13980989,27962001,

%U 55924027,111848079,223696185,447392397,894784823,1789569675,3579139381,7158278793,14316557619

%N a(0)=0, a(n) = 2*(a(n-1) + ceiling(n/2)) - 1 for n>0.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,-3,2).

%F G.f.: x*(x^2+1)/((x+1)*(1-2*x)*(x-1)^2).

%F a(n) = floor(2^n*5/3) - n - 1.

%F a(n) = A081254(n+1) - n - 1.

%F a(n) = a(n-4) + A250777(n-3).

%t LinearRecurrence[{3, -1, -3, 2}, {0, 1, 3, 9}, 40] (* _Amiram Eldar_, Jan 24 2025 *)

%Y Cf. A081254, A109613, A250777.

%K nonn,easy

%O 0,3

%A _Paul Curtz_, Jan 23 2025