OFFSET
0,2
COMMENTS
Results from applying a Chebyshev transform after an inverse Catalan transform to 1/(1-3x). 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 (3,-1,-3,-1)
FORMULA
a(n)=3a(n-1)-a(n-2)-3a(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)3^(n-2k-j)}}.
MATHEMATICA
LinearRecurrence[{3, -1, -3, -1}, {1, 3, 7, 15}, 34] (* James C. McMahon, Jan 01 2024 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Dec 04 2004
STATUS
approved