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A201970
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G.f. satisfies: A(x) = 1 + x*A(x)^2 + x^2/A(x)^3.
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1
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1, 1, 3, 4, 11, 53, 146, 366, 1563, 5837, 16720, 59917, 246090, 828157, 2773984, 11056545, 41539923, 142602611, 536781500, 2103092222, 7632057148, 27948758125, 108960963441, 413531196001, 1523673835870, 5833675306068, 22596747340839, 85028853983908, 322415760345476
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OFFSET
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0,3
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COMMENTS
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This sequence consists entirely of positive integers, but negative coefficients appear in G(x) where G(x) = 1 + x*G(x)^2 + x^2/G(x)^4.
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LINKS
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FORMULA
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G.f. satisfies: x^2 = A(x)^4 - A(x)^3 - x*A(x)^5.
a(n) ~ s*sqrt((2*r + s^5) / (Pi*(6*r + s^5))) / (2*n^(3/2)*r^n), where r = 0.2481615785281025222129020972009425192154180157568... and s = 2.036459583599244077761952153978454195241402482624... are roots of the system of equations 1 + r^2/s^3 + r*s^2 = s, 2*r*s = 1 + 3*r^2/s^4. - Vaclav Kotesovec, Nov 18 2017
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EXAMPLE
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G.f.: A(x) = 1 + x + 3*x^2 + 4*x^3 + 11*x^4 + 53*x^5 + 146*x^6 +...
Related expansions begin:
A(x)^2 = 1 + 2*x + 7*x^2 + 14*x^3 + 39*x^4 + 152*x^5 + 480*x^6 +...
1/A(x)^3 = 1 - 3*x - 3*x^2 + 14*x^3 - 6*x^4 - 114*x^5 + 133*x^6 +...
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PROG
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(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+x*A^2+x^2/(A+x*O(x^n))^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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