A327137 Numbers k such that sin(2k) > sin(2k+2) > sin(2k+4) < sin(2k+6).

7, 10, 13, 16, 29, 32, 35, 38, 51, 54, 57, 60, 73, 76, 79, 82, 95, 98, 101, 104, 117, 120, 123, 126, 139, 142, 145, 148, 161, 164, 167, 170, 183, 186, 189, 192, 205, 208, 211, 214, 227, 230, 233, 236, 249, 252, 255, 258, 271, 274, 277, 280, 293, 296, 299

Offset

1,1

Comments

The sequences A026317, A327136, A327137 partition the nonnegative integers.

Links

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

Example

(sin 2, sin 4, ...) = (0.9, -0.7, -0.2, 0.9, -0.5, ...) approximately, so that the differences, in sign, are - + + -  + + - - + - - + ..., with "+" in places 2,3,5,6,... (A026317), "- +" starting in places 1,4,8,11,... (A327136), and "- - +" starting in places 7,10,13,16,... (A327137).

Mathematica

z = 500; f[x_] := f[x] = Sin[2 x]; t = Range[1, z];
Select[t, f[#] < f[# + 1] &]    (* A026317 *)
Select[t, f[#] > f[# + 1] < f[# + 2] &]  (* A327136 *)
Select[t, f[#] > f[# + 1] > f[# + 2] < f[# + 3] &]   (* A327137 *)

Crossrefs

Cf. A026309, A246303, A026317.

Sequence in context: A154487 A023390 A096678 * A026319 A120153 A226969

Adjacent sequences: A327134 A327135 A327136 * A327138 A327139 A327140

Keyword

nonn,easy

Author

Clark Kimberling, Aug 23 2019

Status

approved