OFFSET
0,1
LINKS
FORMULA
a(n) = ((5+sqrt(3))*(4+sqrt(3))^n+(5-sqrt(3))*(4-sqrt(3))^n)/2.
G.f.: (5-17*x)/(1-8*x+13*x^2).
MATHEMATICA
LinearRecurrence[{8, -13}, {5, 23}, 20] (* Harvey P. Dale, Aug 25 2017 *)
PROG
(Magma) [ n le 2 select 18*n-13 else 8*Self(n-1)-13*Self(n-2): n in [1..20] ];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Klaus Brockhaus, Jul 18 2009
STATUS
approved