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%I #20 Mar 19 2015 15:39:09
%S 0,1,5,6,7,11,12,13,14,18,19,20,24,25,26,30,31,32,37,38,39,43,44,45,
%T 49,50,51,55,56,57,58,62,63,64,68,69,70,74,75,76,81,82,83,87,88,89,93,
%U 94,95,99,100,101,102,106,107,108,112,113,114,118,119,120,125,126,127,131,132
%N Nonnegative integers n for which cos(n) is positive.
%C Nonnegative integers n satisfying sin(n)<sec(n). - _Clark Kimberling_, Aug 26 2014
%C This is proved by taking sec(n)=1/cos(n), therefore considering sin(n)*cos(n)<1 for cos(n)>0 and sin(n)*cos(n)>1 for cos(n)<0. Since sin(n)*cos(n)=sin(2n)/2, the first case becomes sin(2n)<2 for cos(n)>0 which is always correct, and the second case becomes sin(2n)>2 for cos(n)<0 which is never correct. - _R. J. Mathar_, Sep 07 2014
%H Danny Rorabaugh, <a href="/A131503/b131503.txt">Table of n, a(n) for n = 1..10000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Cosine.html">Cosine</a>
%t Select[Range[150],Cos[#]>0&] (* _Harvey P. Dale_, Feb 02 2012 *)
%o (Sage) [i for i in range(200) if cos(i)>0] # _Danny Rorabaugh_, Mar 19 2015
%o (PARI) lista(nn) = for (n=0, nn, if (cos(n) > 0, print1(n, ", "))); \\ _Michel Marcus_, Mar 19 2015
%K easy,nonn
%O 1,3
%A Stephen Casey (hexomino(AT)gmail.com), Aug 13 2007
%E 0 inserted by _R. J. Mathar_, Sep 06 2014