OFFSET
0,2
FORMULA
a(n) = A068913(5,n).
a(n) = 6*a(n-2) - 9*a(n-4) + 2*a(n-6).
a(n) = 2^n for n < 6.
G.f.: ((1-x)^2*(1+x)^2*(1+2*x)) / ((1-2*x^2)*(1-4*x^2+x^4)).
a(2*n+1) = 2*a(2*n).
a(n) = Sum_{k=0..n} A214846(n-k, k). - Philippe Deléham, Mar 25 2013
MATHEMATICA
nn=35; CoefficientList[Series[(1+2x)(1-x^2)^2/(1-6x^2+9x^4-2x^6), {x, 0, nn}], x] (* Geoffrey Critzer, Jan 14 2014 *)
CROSSREFS
KEYWORD
nonn,walk,easy
AUTHOR
Philippe Deléham, Mar 15 2013
EXTENSIONS
a(34) corrected by Sean A. Irvine, May 19 2019
STATUS
approved