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A083812
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4n-1 is the digit reversal of n-1.
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4
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18, 198, 1998, 19998, 199998, 1999998, 19999998, 199999998, 199999998, 1999999998, 19999999998, 199999999998, 1999999999998, 19999999999998, 199999999999998
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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
| a(n) = 2*(10^n - 1).
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EXAMPLE
| 18 -1 = 17, 4*18 - 1 = 71.
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CROSSREFS
| Cf. A000042, A083811.
Sequence in context: A060532 A073397 A020920 * A086573 A097515 A177358
Adjacent sequences: A083809 A083810 A083811 * A083813 A083814 A083815
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KEYWORD
| base,nonn
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AUTHOR
| Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), May 08 2003
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