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Search: id:A120970
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| A120970 |
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G.f. satisfies: A(x/A(x)^2) = 1 + x ; thus A(x) = 1 + series_reversion(x/A(x)^2). |
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+0
6
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| 1, 1, 2, 9, 60, 504, 4946, 54430, 655362, 8496454, 117311198, 1711459903, 26228829200, 420370445830, 7021029571856, 121859518887327, 2192820745899978, 40831103986939664, 785429260324068156
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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G.f. satisfies: A(x) = 1 + x*B(x)^2 = 1 + (1 + x*C(x)^2 )^2 where B(x) and C(x) satisfy: C(x) = B(x)*B(A(x)-1), B(x) = A(A(x)-1), B(A(x)-1) = A(B(x)-1), B(x/A(x)^2) = A(x), B(x) = A(x*B(x)^2), and B(x) is g.f. of A120971.
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PROGRAM
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(PARI) {a(n)=local(A=[1, 1]); for(i=2, n, A=concat(A, 0); A[ #A]=-Vec(subst(Ser(A), x, x/Ser(A)^2))[ #A]); A[n+1]}
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CROSSREFS
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Cf. A120971; variants: A120972, A120974, A120976, A030266, A067145, A107096.
Sequence in context: A005364 A009636 A116364 this_sequence A111558 A001193 A120014
Adjacent sequences: A120967 A120968 A120969 this_sequence A120971 A120972 A120973
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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), Jul 20 2006
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