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Search: id:A083812
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| A083812 |
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4n-1 is the digit reversal of n-1. |
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+0
5
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| 18, 198, 1998, 19998, 199998, 1999998, 19999998, 199999998, 199999998, 1999999998, 19999999998, 199999999998, 1999999999998, 19999999999998, 199999999999998
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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1. a(n) = 18 + 180 + 1800+ ...+ up to n terms. a(n) = sum of n terms of the geometric progression with the first term 18 and common ratio 10. 2. a(n) = 18*A000042(n).( the unary sequence).
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FORMULA
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a(n) = 2*(10^n - 1).
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EXAMPLE
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18 -1 = 17, 4*18 - 1 = 71.
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CROSSREFS
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Cf. A000042, A083811.
Sequence in context: A060532 A073397 A020920 this_sequence A086573 A097515 A026881
Adjacent sequences: A083809 A083810 A083811 this_sequence A083813 A083814 A083815
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 08 2003
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