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A320474
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a(n) = floor(x(n)), where (x(n),y(n)) are defined by the Chirikov "standard map" y(n) = y(n-1) + sin(x(n-1)), x(n) = x(n-1) + y(n), with x(0)=y(0)=1.
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0
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1, 2, 4, 6, 7, 9, 11, 12, 13, 15, 17, 18, 20, 22, 24, 25, 26, 28, 30, 31, 32, 34, 36, 37, 38, 40, 42, 43, 45, 47, 49, 50, 51, 53, 55, 56, 57, 59, 61, 62, 63, 65, 67, 68, 70, 71, 74, 75, 76, 78, 80, 81, 83, 85, 87, 88, 89, 91, 93, 94, 95, 96, 99, 100, 101, 103, 105, 106, 108, 110, 112, 113, 114, 116, 118, 119, 120, 122
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OFFSET
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0,2
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COMMENTS
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The Chirikov map is an example of a nonlinear dynamical system which can exhibit chaotic behavior. Most such maps do not easily lead to integer sequences, but this map does.
Note that some websites reduce x(n) mod 2*Pi, but this version does not.
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REFERENCES
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H. A. Lauwerier, Two-dimensional iterative maps, Chapter 4 of A. V. Holden, ed., Chaos, Princeton, 1986. See Eq. (4.67).
E. N. Lorenz, The Essence of Chaos, Univ. Washington Press, 1993. See p 191.
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LINKS
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Roderick V. Jensen, Classical chaos, American Scientist 75.2 (1987): 168-181. See Eq. (2), (3).
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EXAMPLE
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The initial values of x(n) and y(n) are
1, 2.841470985, 4.978578409, 6.150905537, 7.191338328, 9.020139937, 11.24262759, 12.49547800, 13.67749516, 15.75571048, 17.78619673, 18.94269021, 20.19218340, 22.41575881, 24.22736856, ...
and
1, 1.841470985, 2.137107424, 1.172327128, 1.040432791, 1.828801609, 2.222487650, 1.252850411, 1.182017163, 2.078215324, 2.030486252, 1.156493480, 1.249493186, 2.223575410, 1.811609751, ...
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MAPLE
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k:=1; M:=120; x[0]:=1; y[0]:=1;
for n from 1 to M do
y[n]:=y[n-1]+k*evalf(sin(x[n-1]));
x[n]:=x[n-1]+y[n];
od:
[seq(x[n], n=0..M)];
[seq(y[n], n=0..M)];
[seq(floor(x[n]), n=0..M)]; # A320494
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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