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A269160
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Formula for Wolfram's Rule 30 cellular automaton: a(n) = n XOR (2n OR 4n).
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37
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0, 7, 14, 13, 28, 27, 26, 25, 56, 63, 54, 53, 52, 51, 50, 49, 112, 119, 126, 125, 108, 107, 106, 105, 104, 111, 102, 101, 100, 99, 98, 97, 224, 231, 238, 237, 252, 251, 250, 249, 216, 223, 214, 213, 212, 211, 210, 209, 208, 215, 222, 221, 204, 203, 202, 201, 200, 207, 198, 197, 196, 195, 194, 193, 448, 455, 462
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OFFSET
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0,2
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COMMENTS
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Take n, write it in binary, see what Rule 30 would do to that state, convert it to decimal: that is a(n). For example, we can see in A110240 that 7 = 111_2 becomes 25 = 11001_2 under Rule 30, which is shown here by a(7) = 25. - N. J. A. Sloane, Nov 25 2016
The sequence is injective: no value occurs more than once.
Fibbinary numbers (A003714) give all integers n>=0 for which a(n) = A048727(n) and for which a(n) = A269161(n).
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LINKS
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Eric Weisstein's World of Mathematics, Rule 30
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FORMULA
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Other identities. For all n >= 0:
a(2*n) = 2*a(n).
For all n >= 1:
A070939(a(n)) - A070939(n) = 2. [The binary length of a(n) is two bits longer than that of n for all nonzero values.]
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MATHEMATICA
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PROG
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(Scheme) (define (A269160 n) (A003987bi n (A003986bi (* 4 n) (* 2 n)))) ;; Where A003986bi and A003987bi are implementation of dyadic functions giving bitwise-OR (A003986) and bitwise-XOR (A003987) of their arguments.
(PARI) a(n) = bitxor(n, bitor(2*n, 4*n)); \\ Michel Marcus, Feb 23 2016
(Python)
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CROSSREFS
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Cf. A110240 (iterates starting from 1).
Cf. A269163 (same sequence sorted into ascending order).
Cf. A269164 (values missing from this sequence).
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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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