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%I #9 Jun 13 2015 00:51:03
%S 18,198,1998,19998,199998,1999998,19999998,199999998,1999999998,
%T 19999999998,199999999998,1999999999998,19999999999998,
%U 199999999999998,1999999999999998,19999999999999998,199999999999999998,1999999999999999998,19999999999999999998
%N 4n-1 is the digit reversal of n-1.
%C 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).
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11, -10).
%F a(n) = 2*(10^n - 1).
%F a(1)=18, a(2)=198, a(n)=11*a(n-1)-10*a(n-2). - _Harvey P. Dale_, Apr 24 2015
%e 18 -1 = 17, 4*18 - 1 = 71.
%t Accumulate[NestList[10#&,18,20]] (* or *) LinearRecurrence[{11,-10},{18,198},20] (* _Harvey P. Dale_, Apr 24 2015 *)
%Y Cf. A000042, A083811.
%K base,nonn
%O 1,1
%A _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003
%E Corrected and extended by _Harvey P. Dale_, Apr 24 2015
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