cp's OEIS Frontend

A137697 a(n) = x(n) * 2^((n mod 2 - 1)/2), with x(n)=Sum(x(k)*x(n-k-1):0<=k x(0)=SQRT(2).

%I A137697 #2 Mar 30 2012 18:50:59
%S A137697 1,2,4,20,56,336,1056,6864,22880,155584,537472,3762304,13312768,
%T A137697 95091200,342328320,2481880320,9051563520,66378132480
%N A137697 a(n) = x(n) * 2^((n mod 2 - 1)/2), with x(n)=Sum(x(k)*x(n-k-1):0<=k<n), x(0)=SQRT(2).
%e A137697 x(1) = 2;
%e A137697 x(2) = 5.6568... = a(2)*SQRT(2);
%e A137697 x(3) = 20;
%e A137697 x(4) = 79.1959... = a(4)*SQRT(2);
%e A137697 x(5) = 336;
%e A137697 x(6) = 1493.4095... = a(6)*SQRT(2).
%Y A137697 Cf. A000108.
%K A137697 nonn
%O A137697 0,2
%A A137697 _Reinhard Zumkeller_, Feb 06 2008