OFFSET
0,2
COMMENTS
Results from applying a Chebyshev transform after an inverse Catalan transform to 1/(1-2x). The inverse Catalan transform maps g(x)->g(x(1-x)) while the Chebyshev transform maps h(x)->(1/(1+x^2))h(x/(1+x^2)).
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,0,-2,-1)
FORMULA
a(n)=2a(n-1)-2a(n-3)-a(n-4); a(n)=sum{k=0..floor(n/2), sum{j=0..floor((n-2k)/2), C(n-k, k)C(n-2k-j, j)2^(n-2k-j)}}.
MATHEMATICA
CoefficientList[Series[(1-x^2)/(1-2x+2x^3+x^4), {x, 0, 80}], x] (* Harvey P. Dale, Mar 14 2011 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Dec 04 2004
STATUS
approved