login
A199691
11*10^n+1.
1
12, 111, 1101, 11001, 110001, 1100001, 11000001, 110000001, 1100000001, 11000000001, 110000000001, 1100000000001, 11000000000001, 110000000000001, 1100000000000001, 11000000000000001, 110000000000000001, 1100000000000000001
OFFSET
0,1
FORMULA
a(n) = 10*a(n-1)-9.
a(n) = 11*a(n-1)-10*a(n-2).
G.f.: 3*(4-7*x)/((1-x)*(1-10*x)).
MATHEMATICA
11 10^Range[0, 20]+1 (* or *) LinearRecurrence[{11, -10}, {12, 111}, 20] (* Harvey P. Dale, Jan 29 2023 *)
PROG
(Magma) [11*10^n+1: n in [0..30]];
CROSSREFS
Sequence in context: A036733 A253091 A123933 * A348150 A077754 A199357
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 09 2011
STATUS
approved