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EXAMPLE
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G.f.: A(x) = x + x^2 + x^3 + 101*x^4 + 2301*x^5 + 82601*x^6 + 3287001*x^7 +...
Let G(x) = A(A(A(A(A(x))))):
G(x) = x + 5*x^2 + 25*x^3 + 625*x^4 + 18125*x^5 + 628125*x^6 + 25390625*x^7 +...
such that G(x) = x + 4*x^2 + x*G(G(G(G(G(x))))):
G(G(G(G(G(x))))) = x + 25*x^2 + 625*x^3 + 18125*x^4 + 628125*x^5 + 25390625*x^6 +...
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PROG
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(PARI) {a(n)=local(A=x+x^2, B=x+4*x^2); for(i=1, n+1, B=x+4*x^2+x*subst(B, x, subst(B, x, subst(B, x, subst(B, x, B+x^2*O(x^n))))));
for(j=1, n+1, A=round((4*A+subst(B, x, serreverse(subst(A, x, subst(A, x, subst(A, x, A+x^2*O(x^n)))))))/5));; polcoeff(A, n)}
for(n=1, 31, print1(a(n), ", "))
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