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Search: id:A014925
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| A014925 |
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Number of zeros in numbers 1 to 111...1 (n+1 digits) |
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+0
6
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| 1, 21, 321, 4321, 54321, 654321, 7654321, 87654321, 987654321, 10987654321, 120987654321, 1320987654321, 14320987654321, 154320987654321, 1654320987654321, 17654320987654321, 187654320987654321
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OFFSET
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1,2
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FORMULA
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a(1)=1, a(n)=n*10^(n-1)+a(n-1). G.f.: x/((1-x)(1-10x)^2).
a(n) = 1/90*10^(n+1)*(n+1)-1/81*10^(n+1)+1/81.
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CROSSREFS
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Cf. A033713.
Sequence in context: A057138 A104759 A138793 this_sequence A000422 A060554 A057610
Adjacent sequences: A014922 A014923 A014924 this_sequence A014926 A014927 A014928
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KEYWORD
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nonn,easy,base
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AUTHOR
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Olivier Gerard (ogerard(AT)ext.jussieu.fr)
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EXTENSIONS
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Better description from Stephen G. Penrice (spenrice(AT)ets.org), Oct 03 2000
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