|
|
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
|
|
|
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
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|