login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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, 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 12:51 EST 2020. Contains 338947 sequences. (Running on oeis4.)