A385015 G.f. A(x) satisfies A(x) = 1 + x*A(x)/A(-x*A(x))^3.
1, 1, 4, 4, -13, -81, -389, -198, 7455, 44515, 198661, 70243, -5428624, -40239313, -218619844, -408542577, 3648305171, 44441073999, 339489511573, 1430556904456, 2122222427956, -35048613488679, -504238969376070, -3684488832562182, -21342732340391295, -67688326964892247
Offset: 0
Keywords
Crossrefs
Programs
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PARI
a(n, k=-1) = if(n*k==0, 0^n, (-1)^n*k*sum(j=1, n, binomial(-n+j+k-1, j-1)*a(n-j, 3*j)/j));
Formula
See A385019.