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A277139 Numbers k such that cos(k) < 0 and cos(k+2) < 0. 4

%I #11 Oct 16 2016 09:46:23

%S 2,8,15,21,27,33,34,40,46,52,59,65,71,77,78,84,90,96,103,109,115,121,

%T 122,128,134,140,147,153,159,165,166,172,178,184,191,197,203,209,210,

%U 216,222,228,235,241,247,253,254,260,266,272,279,285,291,297,298,304

%N Numbers k such that cos(k) < 0 and cos(k+2) < 0.

%C Guide to related sequences (a four-way splitting of the natural numbers):

%C A277136: cos(k) > 0 and cos(k+2) > 0

%C A277137: cos(k) > 0 and cos(k+2) < 0

%C A277138: cos(k) < 0 and cos(k+2) > 0

%C A277139: cos(k) < 0 and cos(k+2) < 0

%H Clark Kimberling, <a href="/A277139/b277139.txt">Table of n, a(n) for n = 1..10000</a>

%t z = 400; f[x_] := Cos[x];

%t Select[Range[z], f[#] > 0 && f[# + 2] > 0 &] (* A277136 *)

%t Select[Range[z], f[#] > 0 && f[# + 2] < 0 &] (* A277137 *)

%t Select[Range[z], f[#] < 0 && f[# + 2] > 0 &] (* A277138 *)

%t Select[Range[z], f[#] < 0 && f[# + 2] < 0 &] (* A277139 *)

%o (PARI) is(n) = cos(n) < 0 && cos(n+2) < 0 \\ _Felix Fröhlich_, Oct 14 2016

%Y Cf. A277136, A277137, A277138, subsequence of A246444.

%K nonn,easy

%O 1,1

%A _Clark Kimberling_, Oct 04 2016

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Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)