OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..300
Index entries for linear recurrences with constant coefficients, signature (40,-144).
FORMULA
a(n) = (9*4^n+36^n)/12.
a(n) = 40*a(n-1)-144*a(n-2). - Colin Barker, May 28 2015
G.f.: -6*x*(20*x-1) / ((4*x-1)*(36*x-1)). - Colin Barker, May 28 2015
MATHEMATICA
LinearRecurrence[{40, -144}, {6, 120}, 20] (* Harvey P. Dale, Jun 14 2024 *)
PROG
(Magma) [(9*4^n+36^n)/12: n in [1..15]]; // Vincenzo Librandi, Jun 30 2011
(PARI) Vec(-6*x*(20*x-1) / ((4*x-1)*(36*x-1)) + O(x^100)) \\ Colin Barker, May 28 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paolo Dominici (pl.dm(AT)libero.it)
STATUS
approved