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A097256
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Numbers whose set of base 10 digits is {0,9}.
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10
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0, 9, 90, 99, 900, 909, 990, 999, 9000, 9009, 9090, 9099, 9900, 9909, 9990, 9999, 90000, 90009, 90090, 90099, 90900, 90909, 90990, 90999, 99000, 99009, 99090, 99099, 99900, 99909, 99990, 99999, 900000, 900009, 900090, 900099, 900900
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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COMMENTS
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n such that there exists a permutation p_1, ..., p_n of 1, ..., n such that i + p_i is a power of 10 for every i.
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LINKS
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FORMULA
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a(2n) = 10*a(n), a(2n+1) = a(2n)+9.
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MAPLE
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MATHEMATICA
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Table[(9/2) Sum[(1 - (-1)^Floor[n/2^i]) 10^i, {i, 0, n}], {n, 0, 30}] (* Wesley Ivan Hurt, Feb 11 2014 *)
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PROG
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(Haskell)
a097256 n = a097256_list !! n
a097256_list = map (* 9) a007088_list
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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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