%I A014431
%S A014431 1,2,2,6,14,42,122,382,1206,3922,12914,43190,145950,498170,1714026,
%T A014431 5940014,20712646,72623266,255875298,905477734,3216853294,11469069258,
%U A014431 41023019098,147166210014,529374272470,1908965352434,6899707805522
%N A014431 a(1) = 1, a(2) = 2, a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-2)*a(2) 
               for n >= 3.
%C A014431 a(n)=2*A025235(n-2) for n>=2.
%F A014431 G.f.: (1+x-sqrt(1-2x-7x^2))/2. - Michael Somos, Jun 08 2000.
%o A014431 (PARI) a(n)=polcoeff((1+x-sqrt(1-2*x-7*x^2+x*O(x^n)))/2,n)
%Y A014431 Sequence in context: A002203 A097341 A142710 this_sequence A142471 A071208 
               A083555
%Y A014431 Adjacent sequences: A014428 A014429 A014430 this_sequence A014432 A014433 
               A014434
%K A014431 nonn
%O A014431 1,2
%A A014431 Clark Kimberling (ck6(AT)evansville.edu) and Wouter Meeussen (wouter.meeussen(AT)pandora.be)
%E A014431 Corrected by T. D. Noe (noe(AT)sspectra.com), Oct 31 2006