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%I #2 Mar 30 2012 18:37:09
%S 1,2,4,12,64,664,13856,584668,49751520,8509625760,2919099754336,
%T 2005648412219832,2758163973596156000,7588978611071894509464,
%U 41769719229784446295570112,459846172005153447271276789620
%N G.f.: 1 = Sum_{n>=0} a(n)*x^n*(1-x)/(1+x)^(2^n).
%C Equals the unsigned row sums of triangle A137156.
%o (PARI) {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k*(1-x)/(1+x+x*O(x^n))^(2^k) ), n)}
%Y Cf. A137156; A001192, A137157, A137158, A137159.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Jan 24 2008