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a(n) = floor(2^n csc(1/n)).
8

%I #9 Apr 06 2020 00:16:32

%S 2,8,24,64,161,385,899,2053,4617,10257,22559,49208,106601,229571,

%T 491884,1049258,2229509,4721020,9966072,20980260,44056840,92306470,

%U 192998784,402769716,839084537,1745260723,3624707293,7517790835,15572342341,32218220725,66583540100

%N a(n) = floor(2^n csc(1/n)).

%H Robert Israel, <a href="/A333186/b333186.txt">Table of n, a(n) for n = 1..3306</a>

%F a(n) = floor(2^n csc(1/n)).

%p seq(floor(2^n*csc(1/n)),n=1..100); # _Robert Israel_, Apr 05 2020

%t z = 50; u = Table[Floor[2^n Csc[1/n]], {n, 1, z}] (* A333186 *)

%t v = Table[Floor[2^n Cot[1/n]], {n, 1, z}] (* A333187 *)

%t u - v (* A333188 *)

%t w = Table[Floor[2^n Csc[1/n] - 2^n Cot[1/n]], {n, 1, z}];

%t u - v - w (* A333189 *)

%Y Cf. A333187, A333188, A333189.

%K nonn,easy

%O 1,1

%A _Clark Kimberling_, Mar 11 2020