OFFSET
0,1
LINKS
FORMULA
a(n) = 20*10^n - 9. - Charles R Greathouse IV, Jan 20 2012
a(0)=11, a(n) = 10*a(n-1) + 81.
From G. C. Greubel, Jun 22 2017: (Start)
G.f.: (11 + 70*x)/( (1-x)*(1-10*x) ).
E.g.f.: 20*exp(10*x) - 9*exp(x). (End)
MATHEMATICA
H[n_]:=10^n+1+Sum[10^i*9, {i, 1, n-1}]; Array[H, 100]
CoefficientList[Series[(11 + 70*x)/( (1-x)*(1-10*x) ), {x, 0, 50}], x] (* G. C. Greubel, Jun 23 2017 *)
Table[10FromDigits[PadRight[{1}, n, 9]]+1, {n, 20}] (* or *) LinearRecurrence[ {11, -10}, {11, 191}, 20] (* Harvey P. Dale, May 18 2021 *)
PROG
(PARI) a(n)=20*10^n-9 \\ Charles R Greathouse IV, Jan 20 2012
CROSSREFS
KEYWORD
nonn,easy,less,base
AUTHOR
José María Grau Ribas, Jan 20 2012
STATUS
approved