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A367749
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E.g.f. satisfies A(x) = exp(x * (1 + x + x^2 + x^3) * A(x^4)).
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3
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1, 1, 3, 13, 73, 501, 4051, 37633, 394353, 4777993, 62569891, 893927541, 13827333433, 234241234813, 4212828738483, 80727388033321, 1641227208417121, 35581993575319953, 810641581182744643, 19416795485684156893, 487647253209539939241
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OFFSET
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0,3
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LINKS
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FORMULA
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a(0) = 1; a(n) = (n-1)! * Sum_{k=0..n-1} (k+1) * a(floor(k/4)) * a(n-1-k) / (floor(k/4)! * (n-1-k)!).
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PROG
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(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=(i-1)!*sum(j=0, i-1, (j+1)*v[j\4+1]*v[i-j]/((j\4)!*(i-1-j)!))); v;
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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