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%I #22 Jan 04 2014 14:40:06
%S 2,3,4,7,12,15,18,23,26,29,34,37,40,45,48,51,54,59,62,65,70,73,76,81,
%T 84,87,92,95,98,103,106,109,114,117,120,125,128,131,136,139,142,147,
%U 150,153,158,161,164,169,172,175,180,183,186,191,194,197
%N Positive integers n for which f(-n-1) < f(-n) < f(-n+1), where f(m) = floor(cot(Pi/(2m))).
%C Conjecture: A223568(k) = 2*A223577(k)-k+1, k=1,2,....
%F Conjecture: a(n) = a(n-1)+a(n-3)-a(n-4) for n>6. G.f.: x*(2*x^17-2*x^16+2*x^5+4*x^4+x^3+x^2+x+2) / ((x-1)^2*(x^2+x+1)). - _Colin Barker_, Jan 03 2014
%t f[n_] := Floor[Cot[Pi/(2 n)]]; Select[Range[2, 200], f[-# - 1] < f[-#] < f[-# + 1] &] (* _T. D. Noe_, Mar 22 2013 *)
%Y Cf. A024812, A024813, A223577.
%K nonn
%O 1,1
%A _L. Edson Jeffery_, Mar 22 2013