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A048725
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a(n) = Xmult(n,5) or rule90(n,1).
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21
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0, 5, 10, 15, 20, 17, 30, 27, 40, 45, 34, 39, 60, 57, 54, 51, 80, 85, 90, 95, 68, 65, 78, 75, 120, 125, 114, 119, 108, 105, 102, 99, 160, 165, 170, 175, 180, 177, 190, 187, 136, 141, 130, 135, 156, 153, 150, 147, 240, 245, 250, 255, 228, 225, 238, 235, 216, 221, 210
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OFFSET
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0,2
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COMMENTS
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The orbit of 1 under iteration of this function is the Sierpinski gasket A038183. It is called "rule 90" because the 8 bits of 90 = 01011010 in binary give bit k of the result as function of the value in {0,...,7} made out of bits k,k+1,k+2 of the input (i.e., floor(input / 2^k) mod 8). - M. F. Hasler, Oct 09 2017
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LINKS
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FORMULA
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EXAMPLE
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n (in binary) | 4n [binary] | n XOR 4n [binary] | [decimal] = a(n)
0 | 0 | 0 | 0
1 | 100 | 101 | 5
10 | 1000 | 1010 | 10
11 | 1100 | 1111 | 15
100 | 10000 | 10100 | 20
101 | 10100 | 10001 | 17
etc.
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MAPLE
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a:= n-> Bits[Xor](n*4, n):
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MATHEMATICA
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PROG
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(Python)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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