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%I #6 Jun 13 2015 00:51:46
%S 1,4,20,100,496,2464,12240,60800,302016,1500224,7452160,37017600,
%T 183879936,913398784,4537185280,22537856000,111953760256,556115206144,
%U 2762427289600,13721985024000,68162110078976,338586089570304
%N Expansion of 1/(1-4x-4x^2-4x^3).
%C 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)}.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,4,4).
%F a(n)=sum{k=0..n, T(n-k, k)4^(n-k)}, T(n, k) = trinomial coefficients (A027907)
%Y Cf. A077828, A077835, A000073.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Feb 15 2005
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