OFFSET
1,2
COMMENTS
Other characterization of the sequence: concatenate pattern (1,3,2) multiplying it by 4 after each concatenation step. Or: Start with 1,3,2, then iteratively append the whole sequence obtained so far multiplied by 4^(length of the sequence divided by 3)
LINKS
FORMULA
If n==2 (mod 3) then a(n) = 3*2^[2*(n-1)/3]; else a(n) = 2^[2*(n-1)/3].
a(n) = 4*a(n-3) for n>3. G.f.: x*(1+x)*(1+2*x)/(1-4*x^3). - Colin Barker, Aug 19 2012
PROG
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
M. F. Hasler, May 15 2008
STATUS
approved