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A083812
4n-1 is the digit reversal of n-1.
4
18, 198, 1998, 19998, 199998, 1999998, 19999998, 199999998, 1999999998, 19999999998, 199999999998, 1999999999998, 19999999999998, 199999999999998, 1999999999999998, 19999999999999998, 199999999999999998, 1999999999999999998, 19999999999999999998
OFFSET
1,1
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).
FORMULA
a(n) = 2*(10^n - 1).
a(1)=18, a(2)=198, a(n)=11*a(n-1)-10*a(n-2). - Harvey P. Dale, Apr 24 2015
EXAMPLE
18 -1 = 17, 4*18 - 1 = 71.
MATHEMATICA
Accumulate[NestList[10#&, 18, 20]] (* or *) LinearRecurrence[{11, -10}, {18, 198}, 20] (* Harvey P. Dale, Apr 24 2015 *)
CROSSREFS
Sequence in context: A060532 A073397 A020920 * A086573 A097515 A177358
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003
EXTENSIONS
Corrected and extended by Harvey P. Dale, Apr 24 2015
STATUS
approved