OFFSET
0,3
COMMENTS
10^(floor((n - 2)/2)) | a(n) for n>=1. - G. C. Greubel, Dec 30 2017
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..825
Index entries for linear recurrences with constant coefficients, signature (10, 90).
FORMULA
G.f.: (1-9*x-81*x^2)/(1-10*x-90*x^2).
a(n+1) = Sum_{k=0..n} A154929(n,k)*9^(n-k).
MATHEMATICA
Join[{1}, LinearRecurrence[{10, 90}, {1, 19}, 20]] (* Harvey P. Dale, Oct 10 2012 *)
CoefficientList[Series[(1 - 9*x - 81*x^2)/(1 - 10*x - 90*x^2), {x, 0, 50}], x] (* G. C. Greubel, Dec 30 2017 *)
PROG
(PARI) x='x+O('x^30); Vec((1-9*x-81*x^2)/(1-10*x-90*x^2)) \\ G. C. Greubel, Dec 30 2017
(Magma) I:=[1, 1, 19]; [1] cat [n le 2 select I[n] else 10*Self(n-1) + 90*Self(n-2): n in [1..30]]; // G. C. Greubel, Dec 30 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Philippe Deléham, Jan 19 2009
STATUS
approved