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Search: id:A138914
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| A138914 |
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G.f. A(x) satisfies: 5*A(x) = A(A(A(A(x)))) + 4*x + x^2 with A(0)=0. |
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+0
4
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| 1, 1, 12, 390, 18304, 1071862, 73349996, 5661162666, 482252816998, 44704184452202, 4465265748489708, 477159108766899654, 54255973609630750372, 6536766146592886952548, 831617552461457925554152
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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A(A(A(A(x)))) is the 4-th self-composition of the g.f. A(x).
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EXAMPLE
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G.f.: A(x) = x + x^2 + 12*x^3 + 390*x^4 + 18304*x^5 + 1071862*x^6 +...
A(A(x)) = x + 2*x^2 + 26*x^3 + 841*x^4 + 39440*x^5 + 2308752*x^6 +...
A(A(A(x))) = x + 3*x^2 + 42*x^3 + 1359*x^4 + 63730*x^5 + 3730610*x^6 +...
A(A(A(A(x)))) = x + 4*x^2 + 60*x^3 + 1950*x^4 + 91520*x^5 + 5359310*x^6 +...
so that 5*A(x) = A(A(A(A(x)))) + 4*x + x^2.
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PROGRAM
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(PARI) {a(n)=local(A=x+x^2, G); if(n<1, 0, for(i=3, n+1, G=x; for(j=1, 4, G=subst(A, x, G+x*O(x^i))); A=A+polcoeff(G, i)*x^i); polcoeff(A, n))}
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CROSSREFS
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Cf. A138739, A138913, A138915, A138916.
Sequence in context: A166183 A024298 A081021 this_sequence A003772 A098602 A000897
Adjacent sequences: A138911 A138912 A138913 this_sequence A138915 A138916 A138917
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Apr 03 2008
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