A169650 a(1) = 3; thereafter a(n) = 3*a(n-1)+2^n-6.

3, 7, 23, 79, 263, 847, 2663, 8239, 25223, 76687, 232103, 700399, 2109383, 6344527, 19066343, 57264559, 171924743, 516036367, 1548633383, 4646948719, 13942943303, 41833024207, 125507461223, 376539160879, 1129651037063, 3389020220047, 10167194877863

Offset: 1

Author

N. J. A. Sloane, Apr 07 2010

Keywords

• nonn

Links

• Todd Silvestri, Table of n, a(n) for n = 1..2095

Crossrefs

Apart from offset, equals A145563 + 3. Arises in analyzing A169648.

Programs

Maple

a:=n->if n=1 then 3 else 3*a(n-1)+2^n-6; fi;

Mathematica

a[n_Integer/;n>=1]:=4*3^(n-1)-2^(n+1)+3 (* Todd Silvestri, Dec 15 2014 *)
RecurrenceTable[{a[1]==3,a[n]==3a[n-1]+2^n-6},a,{n,30}] (* Harvey P. Dale, Jan 22 2018 *)

Formula

a(n) = 4*3^(n-1)-2^(n+1)+3. - Todd Silvestri, Dec 15 2014