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a(n) = floor(abs(cos(n)/cos(2n))).
2

%I #10 Jun 15 2018 02:52:08

%S 1,1,0,1,4,0,1,5,0,1,2,0,1,1,0,4,1,0,5,1,0,1,1,1,0,1,3,0,1,6,0,1,2,0,

%T 1,1,0,4,1,0,6,1,0,1,1,1,0,1,3,0,1,7,0,1,2,0,1,1,0,4,1,0,7,1,0,1,1,1,

%U 0,1,3,0,1,8,0,1,2,0,1,1,0,3,1,0,9,1,0,1,1,1,0,1,2,0,1,11,0,1,2,0,1,1,0,3

%N a(n) = floor(abs(cos(n)/cos(2n))).

%H Harry J. Smith, <a href="/A065623/b065623.txt">Table of n, a(n) for n = 0..1000</a>

%e a(10) = floor(abs(cos(10)/cos(20))) = floor(abs(-2.05613)) = floor(2.056) = 2.

%t Table[Floor[Abs[Cos[n]/Cos[2n]]],{n,0,110}] (* _Harvey P. Dale_, Oct 11 2012 *)

%o (PARI) { for (n=0, 1000, a=floor(abs(cos(n)/cos(2*n))); write("b065623.txt", n, " ", a) ) } \\ _Harry J. Smith_, Oct 24 2009

%Y Cf. A065624.

%K nonn

%O 0,5

%A Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Nov 07 2001