OFFSET
0,4
COMMENTS
Hankel transform is A160569(n+1).
FORMULA
G.f.: (1-x^2-sqrt(1-2x^2-12x^3+x^4))/(6*x^3);
G.f.: 1/(1-x^2-3*x^3/(1-x^2-3*x^3/(1-x^2-3*x^3/(1-x^2-3*x^3/(1-... (continued fraction).
a(n)=sum{k=0..floor(n/2), C(n-k,2n-4k)*3^(n-2k)*A000108(n-2k)};
a(n)=sum{k=0..n, C(n-k/2,2(n-k))*3^(n-k)*A000108(n-k)*(1+(-1)^k)/2};
a(n)=sum{k=0..n, C((n+k)/2,2k)*3^k*A000108(k)(1+(-1)^(n-k))/2}.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, May 19 2009
STATUS
approved