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%I #6 Jan 25 2015 16:38:17
%S 1,0,-1,1,2,5,8,13,20,38,86,215,526,1230,2762,6115,13670,31294,73258,
%T 173644,412612,978074,2313060,5472523,12989654,30974176,74174934,
%U 178173000,428776280,1033084378,2491843724,6018491615,14559411886,35279687544
%N a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5.
%F G.f.: 1/2 - sqrt(-12*x^4+4*x^3+4*x^2-4*x+1)/2. - _Vaclav Kotesovec_, Jan 25 2015
%F Recurrence: n*a(n) = 2*(2*n-3)*a(n-1) - 4*(n-3)*a(n-2) - 2*(2*n-9)*a(n-3) + 12*(n-6)*a(n-4). - _Vaclav Kotesovec_, Jan 25 2015
%t nmax = 30; aa = ConstantArray[0,nmax]; aa[[1]] = 1; aa[[2]] = 0; aa[[3]] = -1; aa[[4]] = 1; Do[aa[[n]] = Sum[aa[[k]]*aa[[n-k]],{k,1,n-1}],{n,5,nmax}]; aa (* _Vaclav Kotesovec_, Jan 25 2015 *)
%K sign
%O 1,5
%A _Clark Kimberling_