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A113312
Expansion of (1+x)^2/(1-2x^2+x^3).
1
1, 2, 3, 3, 4, 3, 5, 2, 7, -1, 12, -9, 25, -30, 59, -85, 148, -229, 381, -606, 991, -1593, 2588, -4177, 6769, -10942, 17715, -28653, 46372, -75021, 121397, -196414, 317815, -514225, 832044, -1346265, 2178313, -3524574, 5702891, -9227461, 14930356, -24157813, 39088173, -63245982, 102334159
OFFSET
0,2
COMMENTS
Diagonal sums of A113310.
FORMULA
a(n)=2a(n-2)-a(n-3); a(n)=sum{k=0..floor(n/2), sum{i=0..n-2k, (-1)^i*C(i+k-2, i)}}.
MATHEMATICA
LinearRecurrence[{0, 2, -1}, {1, 2, 3}, 50] (* Harvey P. Dale, May 19 2014 *)
CROSSREFS
Sequence in context: A086925 A088858 A372627 * A334954 A053475 A140605
KEYWORD
easy,sign
AUTHOR
Paul Barry, Oct 25 2005
STATUS
approved