A198962 5*9^n-1.

4, 44, 404, 3644, 32804, 295244, 2657204, 23914844, 215233604, 1937102444, 17433922004, 156905298044, 1412147682404, 12709329141644, 114383962274804, 1029455660473244, 9265100944259204, 83385908498332844, 750473176484995604

Offset: 0

Author

Vincenzo Librandi, Nov 01 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (10,-9).

Programs

Magma

[5*9^n-1: n in [0..20]]

Mathematica

5*9^Range[0,30]-1 (* or *) LinearRecurrence[{10,-9},{4,44},30] (* Harvey P. Dale, Oct 20 2019 *)

Formula

a(n) = 4*A138894(n).

a(n) = 9*a(n-1)+8, n>0.

a(n) = 10*a(n-1)-9*a(n-2), n>1.

G.f. ( 4+4*x ) / ( (9*x-1)*(x-1) ). - R. J. Mathar, Nov 01 2011