

A277139


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


4



2, 8, 15, 21, 27, 33, 34, 40, 46, 52, 59, 65, 71, 77, 78, 84, 90, 96, 103, 109, 115, 121, 122, 128, 134, 140, 147, 153, 159, 165, 166, 172, 178, 184, 191, 197, 203, 209, 210, 216, 222, 228, 235, 241, 247, 253, 254, 260, 266, 272, 279, 285, 291, 297, 298, 304
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OFFSET

1,1


COMMENTS

Guide to related sequences (a fourway 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 FrÃ¶hlich, Oct 14 2016


CROSSREFS

Cf. A277136, A277137, A277138, subsequence of A246444.
Sequence in context: A140973 A065907 A031272 * A213082 A246304 A063286
Adjacent sequences: A277136 A277137 A277138 * A277140 A277141 A277142


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Oct 04 2016


STATUS

approved



