Voozh

A117672

Numbers k such that |cos(k)*cos(k+2)| < (cos(k+1))^2.

2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17, 18, 21, 24, 25, 27, 28, 30, 31, 33, 34, 36, 37, 39, 40, 43, 46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 65, 68, 69, 71, 72, 74, 75, 77, 78, 80, 81, 83, 84, 87, 90, 91, 93, 94, 96, 97, 99, 100, 102, 103, 105, 106, 109, 112, 113, 115

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

What is the density of the sequence? I am convinced that this sequence has the same density as A026313.

LINKS

Chris R. Rehmann, Table of n, a(n) for n = 1..10000

EXAMPLE

|cos(5)*cos(7)| < (cos(6))^2, therefore 5 is in the sequence.

MATHEMATICA

Select[Range[120], Abs[Cos[ # ]*Cos[ # + 2]] < Cos[ # + 1]^2 &]

PROG