A246304 Numbers k such that cos(k) > cos(k+1) < cos(k+2).

2, 8, 15, 21, 27, 34, 40, 46, 52, 59, 65, 71, 78, 84, 90, 96, 103, 109, 115, 122, 128, 134, 140, 147, 153, 159, 166, 172, 178, 184, 191, 197, 203, 209, 216, 222, 228, 235, 241, 247, 253, 260, 266, 272, 279, 285, 291, 297, 304, 310, 316, 323, 329, 335, 341

Offset: 1

Author

Clark Kimberling, Aug 22 2014

Keywords

• nonn
• easy

Comments

The sequences A246303, A246304, A246305, A246306 partition the nonnegative integers.

Links

• Clark Kimberling, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A026303, A246305, A246306, A026311 (complement of A246303).

Programs

Mathematica

z = 500; f[x_] := f[x] = Cos[x]; t = Range[0, z];
Select[t, f[#] < f[# + 1] &]  (* A246303 *)
Select[t, f[#] > f[# + 1] < f[# + 2] &]  (* A246304 *)
Select[t, f[#] > f[# + 1] > f[# + 2] < f[# + 3] &]  (* A246305 *)
Select[t, f[#] > f[# + 1] > f[# + 2] > f[# + 3] < f[# + 4] &] (* A246306 *)
Flatten[Position[Partition[Cos[Range[400]],3,1],?(#[[1]]>#[[2]] && #[[2]]< #[[3]]&),{1},Heads->False]] (* _Harvey P. Dale, Apr 23 2015 *)