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Decimal expansion of the absolute minimum of cos(x)+cos(2x)+cos(3x)+cos(4x).
3

%I #12 Dec 05 2016 10:40:13

%S 1,5,1,9,5,5,7,8,8,1,6,4,2,8,4,8,2,5,1,3,6,9,4,2,6,8,1,1,3,2,9,8,5,0,

%T 7,3,4,5,5,8,7,7,8,4,3,8,3,3,6,1,2,2,9,4,5,2,2,9,8,8,5,5,0,0,2,8,5,0,

%U 6,9,8,9,3,4,7,1,3,4,1,7,9,3,5,7,7,0,4,2,5,5,5,8,2,7,4,8,0,5,4

%N Decimal expansion of the absolute minimum of cos(x)+cos(2x)+cos(3x)+cos(4x).

%C See A196361 for a guide to related sequences.

%e x=1.002750019227300659428346483723194...

%e min=-1.519557881642848251369426811329...

%t n = 4; f[t_] := Cos[t]; s[t_] := Sum[f[k*t], {k, 1, n}];

%t x = N[Minimize[s[t], t], 110]; u = Part[x, 1]

%t v = 2 Pi - t /. Part[x, 2]

%t RealDigits[u] (* A198671 *)

%t RealDigits[v] (* A198672 *)

%t Plot[s[t], {t, -3 Pi, 3 Pi}]

%t (* Second program: *)

%t Root[-125 + 600x + 1227x^2 + 512x^3, 1] // RealDigits[#, 10, 99]& // First (* _Jean-François Alcover_, Feb 19 2013 *)

%Y Cf. A196361.

%K nonn,cons

%O 1,2

%A _Clark Kimberling_, Oct 28 2011