OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,1).
FORMULA
a(n)=4a(n-1)-6a(n-2)+4a(n-3)+a(n-4); a(n)=sum{k=0..n, sum{j=0..n-k, C(k,2j)C(n-k,2j)*2^j}}.
MATHEMATICA
CoefficientList[Series[(1-x)^2/((1-x)^4-2x^4), {x, 0, 50}], x] (* or *) LinearRecurrence[{4, -6, 4, 1}, {1, 2, 3, 4}, 50] (* Harvey P. Dale, Jul 20 2021 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, May 14 2006
STATUS
approved