This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A327140 #15 Jun 21 2021 06:03:35 %S A327140 3,6,9,22,25,28,31,44,47,50,53,66,69,72,75,88,91,94,97,110,113,116, %T A327140 119,132,135,138,141,154,157,160,163,179,182,185,188,201,204,207,210, %U A327140 223,226,229,232,245,248,251,254,267,270,273,276,289,292,295,298,311 %N A327140 Numbers k such that cos(2k) > cos(2k+2) > cos(2k+4) < cos(2k+6). %C A327140 The sequences A327138, A327139, A327140 partition the positive integers. %H A327140 Clark Kimberling, <a href="/A327140/b327140.txt">Table of n, a(n) for n = 1..10000</a> %e A327140 (cos 2, cos 4, ...) = (-0.4, -0.6, 0.9, -0.1, -0.8, ...) approximately, so that the differences, in sign, are - + - - + - - + - - + +, with "+" in places 2,5,8,11,12, ... (A327138), "- +" starting in places 1,4,7,10,13,... (A327139), and "- - +" starting in places 3,6,9,22,25,... (A327140). %t A327140 z = 500; f[x_] := f[x] = Cos[2 x]; t = Range[1, z]; %t A327140 Select[t, f[#] < f[# + 1] &] (* A327138 *) %t A327140 Select[t, f[#] > f[# + 1] < f[# + 2] &] (* A327139 *) %t A327140 Select[t, f[#] > f[# + 1] > f[# + 2] < f[# + 3] &] (* A327140 *) %Y A327140 Cf. A026309, A246303, A026317, A327138. %K A327140 nonn,easy %O A327140 1,1 %A A327140 _Clark Kimberling_, Aug 23 2019