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A088368
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G.f. satisfies: A(x) = Sum_{n>=0} n!*x^n*A(x)^n.
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2
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1, 1, 3, 13, 69, 421, 2867, 21477, 175769, 1567273, 15213955, 160727997, 1846282381, 23013527421, 310284575683, 4506744095141, 70199956070705, 1167389338452753
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| a(n) = number of partitions of [n] into sets of noncrossing lists. For example, a(4) = 69 counts the 73 partitions of [n] into sets of lists (A000262) except for 13-24, 13-42, 31-24, 31-42 which are crossing. - David Callan (callan(AT)stat.wisc.edu), Jul 25 2008
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LINKS
| David Callan, Sets, Lists and Noncrossing Partitions .
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FORMULA
| G.f.: A(x) = (1/x)*Series_Reversion( x/[Sum_{n>=0} n!*x^n] ).
G.f. satisfies: A(x) = 1/(1 - x*A(x)/(1 - x*A(x)/(1 - 2*x*A(x)/(1 - 2*x*A(x)/(1 - 3*x*A(x)/(1 - 3*x*A(x)/(1 - 4*x*A(x)/(1 - ...)))))))), a recursive continued fraction.
G.f. satisfies: A(x/F(x)) = F(x) where F(x) = Sum_{n>=0} n!*x^n.
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EXAMPLE
| G.f.: A(x) = 1 + x + 3*x^2 + 13*x^3 + 69*x^4 + 421*x^5 + 2867*x^6 +...
where
A(x) = 1 + x*A(x) + 2!*x^2*A(x)^2 + 3!*x^3*A(x)^3 + 4!*x^4*A(x)^4 +...
Related expansions:
A(x)^2 = 1 + 2*x + 7*x^2 + 32*x^3 + 173*x^4 + 1058*x^5 +...
A(x)^3 = 1 + 3*x + 12*x^2 + 58*x^3 + 321*x^4 + 1977*x^5 +...
A(x)^4 = 1 + 4*x + 18*x^2 + 92*x^3 + 523*x^4 + 3256*x^5 +...
A(x)^5 = 1 + 5*x + 25*x^2 + 135*x^3 + 790*x^4 + 4986*x^5 +...
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MATHEMATICA
| FrequencyDistribution[list_List] := Module[{set = Union[list]}, Table[{set[[i]], Count[list, set[[i]]]}, {i, Length[set]}]]; a[0] = 1; a[n_]/; n>=1 := a[n] = Apply[Plus, Module[{frequencies}, Map[(frequencies=Map[Last, FrequencyDistribution[ # ]]; Sum[frequencies]!*Apply[Multinomial, frequencies]* Product[Map[a, # ]])&, Partitions[n]-1 ]]] Table[a[n], {n, 0, 15}] - David Callan (callan(AT)stat.wisc.edu), Jul 25 2008
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PROG
| (PARI) {a(n)=polcoeff(1/x*serreverse(x/sum(m=0, n, m!*x^m)+x^2*O(x^n)), n)}
(PARI) /* Recursive continued fraction: */
{a(n)=local(A=1+x, CF=1+x*O(x^(n+2))); for(i=1, n, for(k=1, n+1, CF=1/(1-((n-k+1)\2+1)*x*A*CF)); A=CF); polcoeff(A, n)}
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CROSSREFS
| Cf. A198916.
Sequence in context: A067145 A088714 A192739 * A196794 A184818 A007808
Adjacent sequences: A088365 A088366 A088367 * A088369 A088370 A088371
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KEYWORD
| nonn
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AUTHOR
| Paul D. Hanna (pauldhanna(AT)juno.com), Sep 28 2003
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