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A119330
Expansion of (1-x)^2/((1-x)^4-2x^4).
2
1, 2, 3, 4, 7, 18, 49, 120, 265, 554, 1155, 2476, 5455, 12138, 26881, 58992, 128689, 280466, 612579, 1341268, 2940151, 6443778, 14111857, 30886632, 67590649, 147934010, 323850531, 709047292, 1552412671, 3398703066, 7440375937
OFFSET
0,2
COMMENTS
Row sums of A119329. Binomial transform of A119332, or (1,1,0,0,2,2,0,0,4,4,...).
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
Sequence in context: A139439 A376735 A352902 * A373392 A084644 A208729
KEYWORD
easy,nonn
AUTHOR
Paul Barry, May 14 2006
STATUS
approved