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1, 9, 89, 991, 9909, 88991, 899911, 9999009, 99990089, 899910991, 8899099911, 99089999009, 990999990091, 8899999911009, 89999999100089, 999999990000991, 9999999900009909, 89999999100088991, 889999991100899911
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n)=sum{k=0..n, (-1)^A010060(2n-2k)*mod(binomial(2n-k, k), 2)10^k}.
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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