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A272066
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a(n) = (10^n-1)^3.
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8
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0, 729, 970299, 997002999, 999700029999, 999970000299999, 999997000002999999, 999999700000029999999, 999999970000000299999999, 999999997000000002999999999, 999999999700000000029999999999, 999999999970000000000299999999999, 999999999997000000000002999999999999
(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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The sum of the digits of a(n) is divisible by 18. For example, 9^3 = 729 and 7 + 2 + 9 = 18 * 1.
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LINKS
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FORMULA
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O.g.f.: 729*x*(1 + 220*x + 1000*x^2)/((1 - x)*(1 - 10*x)*(1 - 100*x)*(1 - 1000*x)).
E.g.f.: (-1 + 3*exp(9*x) - 3*exp(99*x) + exp(999*x))*exp(x). (End)
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EXAMPLE
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n| a(n) can be divided into 3 parts for n > 1.
-+--------------------------------------------
1| 72 9
2| 9 702 99
3| 99 7002 999
4| 999 70002 9999
(End)
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MAPLE
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MATHEMATICA
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PROG
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(Ruby)
(0..n).each{|i| p ('9' * i).to_i ** 3}
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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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