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%I #10 Oct 09 2023 11:20:46
%S 1,2,-7,74,-820,10196,-134785,1860668,-26508457,386843804,-5753126477,
%T 86878155652,-1328593620692,20533664196478,-320220157730975,
%U 5032648114664896,-79629405527982623,1267425784159379572,-20279086501234998596,325989622456860054852
%N G.f. A(x) satisfies A(x) = (1 + x / A(x)^(9/2)) / (1 - x).
%F a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(11*k/2-1,k) * binomial(9*k/2-1,n-k) / (11*k/2-1).
%o (PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(11*k/2-1, k)*binomial(9*k/2-1, n-k)/(11*k/2-1));
%Y Cf. A366400, A366401, A366402, A366403, A366404, A366405, A366406.
%K sign
%O 0,2
%A _Seiichi Manyama_, Oct 09 2023