A198796 3*6^n-1.

2, 17, 107, 647, 3887, 23327, 139967, 839807, 5038847, 30233087, 181398527, 1088391167, 6530347007, 39182082047, 235092492287, 1410554953727, 8463329722367, 50779978334207, 304679870005247, 1828079220031487

Offset: 0

Author

Vincenzo Librandi, Oct 30 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 (7,-6).

Programs

Magma

[3*6^n-1: n in [0..30]];

Mathematica

Table[3*6^n-1,{n,0,30}] (* or *) LinearRecurrence[{7,-6},{2,17},30] (* Harvey P. Dale, May 22 2016 *)

Formula

a(n) = 6*a(n-1)+5. a(n) = 7*a(n-1)-6*a(n-2), n>1.

G.f.: ( 2+3*x ) / ( (6*x-1)*(x-1) ). - R. J. Mathar, Oct 30 2011