OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (3,4).
FORMULA
a(n+1)-4*a(n) = period 2: repeat [5, -5].
G.f.: x*(1 + 6*x)/(1 - 3*x - 4*x^2). - Ilya Gutkovskiy, May 11 2016
From Klaus Purath, Aug 03 2020: (Start)
a(n) = 30*4^(n-3) + a(n-2), n>2.
a(n+2) = 3*a(n+1) + 4*a(n). (End)
MATHEMATICA
a[n_] := (2*4^n - (-1)^n); Array[a, 25, 0] (* Robert G. Wilson v, Aug 13 2011 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, May 26 2008
EXTENSIONS
Extended and offset changed from 0 to 1 by Vincenzo Librandi, Aug 09 2011
STATUS
approved