OFFSET
0,1
COMMENTS
a(n) gives the combined total number of n digit numbers [preceding zeros allowed] in base 10 and 11.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..900
Index entries for linear recurrences with constant coefficients, signature (21,-110).
FORMULA
G.f.: 1/(1-10*x) + 1/(1-11*x). - Vincenzo Librandi, Feb 06 2013
From Elmo R. Oliveira, Sep 12 2024: (Start)
E.g.f.: exp(10*x)*(exp(x) + 1).
a(n) = 21*a(n-1) - 110*a(n-2) for n > 1. (End)
MATHEMATICA
CoefficientList[Series[1/(1 - 10 x) + 1/(1 - 11 x), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 06 2013 *)
LinearRecurrence[{21, -110}, {2, 21}, 20] (* Harvey P. Dale, Aug 27 2020 *)
PROG
(Magma) [10^n+11^n: n in [0..30]]; // Vincenzo Librandi, Feb 06 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Avik Roy (avik_3.1416(AT)yahoo.co.in), Jan 29 2009
STATUS
approved