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A270307
Expansion of -(4*x^3+8*x^2+4*x+1)/(2*x^4+4*x^3+2*x^2-x-1).
1
1, 3, 7, 7, 21, 27, 57, 95, 169, 303, 529, 943, 1665, 2943, 5217, 9215, 16321, 28863, 51073, 90367, 159873, 282879, 500481, 885503, 1566721, 2771967, 4904449, 8677375, 15352833, 27163647, 48060417, 85032959, 150448129, 266186751, 470962177
OFFSET
0,2
FORMULA
a(n) = (n+1)*Sum_{k=0..n}(Sum_{l=0..n-k}(binomial(k+1,l)*2^l*(-1)^(n-l-k)*binomial(n-2*l,n-l-k))/(k+1)).
MATHEMATICA
LinearRecurrence[{-1, 2, 4, 2}, {1, 3, 7, 7}, 50] (* Harvey P. Dale, Apr 11 2017 *)
PROG
(Maxima)
a(n):=(n+1)*sum(sum(binomial(k+1, l)*2^l*(-1)^(n-l-k)*binomial(n-2*l, n-l-k), l, 0, n-k)/(k+1), k, 0, n);
CROSSREFS
Cf. A001405.
Sequence in context: A212286 A157102 A226512 * A261480 A121172 A341539
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, Mar 15 2016
STATUS
approved