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A344511
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a(n) = Sum_{k >= 0} sign(d_k) * 2^k for any number n with decimal expansion Sum_{k >= 0} d_k * 10^k.
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2
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0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3
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OFFSET
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0,11
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COMMENTS
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The binary expansion of a(n) encodes the nonzero digits of the decimal expansion of n.
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LINKS
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FORMULA
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EXAMPLE
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For n = 20!:
- 2432902008176640000 is the decimal expansion of 20!, so
1111101001111110000 is the binary expansion of a(20!),
- a(20!) = 513008.
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PROG
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(PARI) a(n) = fromdigits(apply(sign, digits(n)), 2)
(Python)
def a(n): return int("".join((('1' if d!='0' else '0') for d in str(n))), 2)
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CROSSREFS
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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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