OFFSET
0,1
COMMENTS
Let A=[1,1,1;2,0,-2;1,-1,1], the 3 X 3 Krawtchouk matrix. Then a(n)=trace(A^n).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,4)
FORMULA
G.f.: (3+2*x)/((1+2*x)*(1-2*x)).
a(n) = (-2)^n+2*2^n.
Recurrence: a(n) = 4a(n-2), a(0)=3, a(1)=2. - Ralf Stephan, Jul 17 2013
PROG
(Magma) [(-2)^n+2*2^n: n in [0..45]]; // Vincenzo Librandi, Jun 11 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 18 2004
STATUS
approved