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A292681
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Rule 6: (000, ..., 111) -> (0, 1, 1, 0, 0, 0, 0, 0), without extending to the right of input bit 0.
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4
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0, 3, 6, 4, 12, 13, 8, 8, 24, 27, 26, 24, 16, 17, 16, 16, 48, 51, 54, 52, 52, 53, 48, 48, 32, 35, 34, 32, 32, 33, 32, 32, 96, 99, 102, 100, 108, 109, 104, 104, 104, 107, 106, 104, 96, 97, 96, 96, 64, 67, 70, 68, 68, 69, 64, 64, 64, 67, 66, 64, 64, 65, 64, 64, 192, 195, 198, 196, 204, 205, 200, 200, 216
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OFFSET
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0,2
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COMMENTS
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Rule 6 is the smallest rule which is even (otherwise infinitely many bits would be switched on at step 1, for any finite starting value) and nontrivial (i.e., does not lead to extinction nor simple reproduction, possibly shifted left or right, of a single-bit initial state).
In the context of elementary cellular automata, one would usually consider one further bit of output (i.e., the cell which has bit 0 of the input as left neighbor). This leads to A292680 which has all terms even, so it is natural to consider this variant.
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LINKS
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EXAMPLE
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n | a(n)
0 = 0[2] | 0[2] = 0
1 = 1[2] | 11[2] = 3 (bits below 001 and 01(0) are on)
2 = 10[2] | 110[2] = 6 (1 below 001 and 010, 0 below 10(0))
3 = 11[2] | 100[2] = 4 (1 below 001, 0 below 011 and 11(0))
4 = 100[2] | 1100[2] = 12 (as n = 1 and n = 2, shifted right once more)
5 = 101[2] | 1101[2] = 13 (1 below 001 and 010 (twice), 0 below 101)
6 = 110[2] | 1000[2] = 8 (as n = 3, shifted right once)
7 = 111[2] | 1000[2] = 8 (1 below 001, 0 below 011, 111 and 11(0)).
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PROG
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(PARI) apply( A292681(n, r=6)=sum(i=0, logint(!n+n<<=1, 2)+1, bittest(r, (n>>i)%8)<<i), [0..60])
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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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