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A109002
Maximal difference between two n-digit numbers.
6
9, 89, 899, 8999, 89999, 899999, 8999999, 89999999, 899999999, 8999999999, 89999999999, 899999999999, 8999999999999, 89999999999999, 899999999999999
OFFSET
1,1
COMMENTS
a(n) = A061601(A178500(n-1)). - Reinhard Zumkeller, May 28 2010
FORMULA
a(n) = (10^n -1) - 10^(n-1), n > 1.
a(n+1) = 10*a(n) + 9. - Reinhard Zumkeller, May 28 2010
G.f.: 9*x - x^2*(-89+80*x) / ( (10*x-1)*(x-1) ). - R. J. Mathar, Oct 29 2011
EXAMPLE
a(1) = 9 - 0 = 9, a(4) = 9999 - 1000 = 8999.
MATHEMATICA
Join[{9}, Table[FromDigits[PadRight[{8}, n, 9]], {n, 2, 20}]] (* or *) LinearRecurrence[{11, -10}, {9, 89, 899}, 20] (* Harvey P. Dale, May 09 2021 *)
PROG
(Magma) [9], [9*10^n-1: n in [1..30]]; // Vincenzo Librandi, Oct 29 2011
(PARI) a(n)=if(n>1, (10^n-1)-10^(n-1), 9) \\ Charles R Greathouse IV, Oct 29 2011
CROSSREFS
Sequence in context: A138288 A370179 A059482 * A142991 A152267 A082147
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Aug 14 2005
STATUS
approved