A277138 Numbers k such that cos(k) < 0 and cos(k+2) > 0.

3, 4, 9, 10, 16, 17, 22, 23, 28, 29, 35, 36, 41, 42, 47, 48, 53, 54, 60, 61, 66, 67, 72, 73, 79, 80, 85, 86, 91, 92, 97, 98, 104, 105, 110, 111, 116, 117, 123, 124, 129, 130, 135, 136, 141, 142, 148, 149, 154, 155, 160, 161, 167, 168, 173, 174, 179, 180, 185

Offset

1,1

Comments

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

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

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

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

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

Links

Clark Kimberling, Table of n, a(n) for n = 1..10000

Mathematica

z = 400; f[x_] := Cos[x];
Select[Range[z], f[#] > 0 && f[# + 2] > 0 &] (* A277136 *)
Select[Range[z], f[#] > 0 && f[# + 2] < 0 &] (* A277137 *)
Select[Range[z], f[#] < 0 && f[# + 2] > 0 &] (* A277138 *)
Select[Range[z], f[#] < 0 && f[# + 2] < 0 &] (* A277139 *)

Prog

(PARI) is(n) = cos(n) < 0 && cos(n+2) > 0 \\ Felix Fröhlich, Oct 14 2016

Crossrefs

Cf. A277136, A277137, A277139, subsequence of A246444.

Sequence in context: A301919 A093513 A047230 * A327282 A126269 A319618

Adjacent sequences: A277135 A277136 A277137 * A277139 A277140 A277141

Keyword

nonn,easy

Author

Clark Kimberling, Oct 04 2016

Status

approved