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A120590
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G.f. satisfies: 4*A(x) = 3 + x + A(x)^3, starting with [1,1,3].
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5
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1, 1, 3, 19, 150, 1326, 12558, 124590, 1278189, 13449205, 144342627, 1573990275, 17389407984, 194228357568, 2189610888840, 24881753664840, 284708154606318, 3277578288381318, 37934510719585350, 441152315040444150
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OFFSET
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0,3
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COMMENTS
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See comments in A120588 for conditions needed for an integer sequence to satisfy a functional equation of the form: r*A(x) = c + b*x + A(x)^n.
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LINKS
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FORMULA
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G.f.: A(x) = 1 + Series_Reversion(1+4*x - (1+x)^3).
G.f.: A(x) = Sum_{n>=0} C(3*n,n)/(2*n+1) * (3+x)^(2*n+1) / 4^(3*n+1), due to Lagrange Inversion.
Recurrence: 13*(n-1)*n*a(n) = 81*(n-1)*(2*n-3)*a(n-1) + 3*(3*n-7)*(3*n-5)*a(n-2). - Vaclav Kotesovec, Oct 19 2012
a(n) ~ sqrt(32-18*sqrt(3))*((81+48*sqrt(3))/13)^n/(12*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 19 2012
G.f.: 4 * sin( arcsin(3 * sqrt(3) * (3 + x) / 16) / 3) / sqrt(3). - Benedict W. J. Irwin, Oct 19 2016
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EXAMPLE
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A(x) = 1 + x + 3*x^2 + 19*x^3 + 150*x^4 + 1326*x^5 + 12558*x^6 +...
A(x)^3 = 1 + 3*x + 12*x^2 + 76*x^3 + 600*x^4 + 5304*x^5 + 50232*x^6 +...
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MATHEMATICA
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FullSimplify[Table[SeriesCoefficient[Sum[Binomial[3*k, k]/(2*k+1)*(3+x)^(2*k+1)/4^(3*k+1), {k, 0, Infinity}], {x, 0, n}] , {n, 0, 20}]] (* Vaclav Kotesovec, Oct 19 2012 *)
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PROG
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(PARI) {a(n)=local(A=1+x+3*x^2+x*O(x^n)); for(i=0, n, A=A-4*A+3+x+A^3); polcoeff(A, n)}
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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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