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A117998
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Decimal number generated by the binary bits of the n-th generation of the Rule 102 elementary cellular automaton.
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3
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1, 6, 20, 120, 272, 1632, 5440, 32640, 65792, 394752, 1315840, 7895040, 17895424, 107372544, 357908480, 2147450880, 4295032832, 25770196992, 85900656640, 515403939840, 1168248930304, 7009493581824, 23364978606080
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OFFSET
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0,2
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COMMENTS
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LINKS
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Eric Weisstein's World of Mathematics, Rule 102
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FORMULA
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Bala's observation is correct, and follows from the formula given below and from the fact that this is the central diagonal of square array A099884.
a(n) = A000079(n) * A001317(n). [See Eric Weisstein's World of Mathematics -link]
a(0) = 1; for n > 0, a(n) = A048726(a(n-1)).
(End)
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EXAMPLE
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1; 1, 1, 0; 1, 0, 1, 0, 0; 1, 1, 1, 1, 0, 0, 0; 1, 0, 0, 0, 1, 0, 0, 0, 0; ...
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MATHEMATICA
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NestList[BitXor[4#, 2#]&, 1, 50] (* Paolo Xausa, Oct 04 2023 *)
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PROG
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(Python)
def A117998(n): return sum((bool(~n&n-k)^1)<<k for k in range(n+1))<<n # Chai Wah Wu, May 03 2023
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CROSSREFS
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Iterates of A048726, starting from a(0) = 1.
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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