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A103771
Expansion of 1/(1-4x-4x^2-4x^3).
0
1, 4, 20, 100, 496, 2464, 12240, 60800, 302016, 1500224, 7452160, 37017600, 183879936, 913398784, 4537185280, 22537856000, 111953760256, 556115206144, 2762427289600, 13721985024000, 68162110078976, 338586089570304
OFFSET
0,2
COMMENTS
The sequence with g.f. 1/(1-r*x-r*x^2-r*x^3) has general term sum{k=0..n, T(n-k,k)r^(n-k)}.
FORMULA
a(n)=sum{k=0..n, T(n-k, k)4^(n-k)}, T(n, k) = trinomial coefficients (A027907)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Feb 15 2005
STATUS
approved