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A221020 Reduced denominators of A179420(n)/n!, where e.g.f. A(x) = Sum_{n>=0} A179420(n)/n! satisfies: A(A(x)) = x*A'(x) with A(0)=0, A'(0)=1. 3
1, 1, 1, 2, 3, 6, 5, 360, 420, 56, 756, 75600, 415800, 2494800, 8424, 1223040, 504504000, 9081072000, 5145940800, 111152321280, 754247894400, 37712394720000, 430747632000, 14454741869568, 319672175961600, 4080179409546240, 14011605115200000, 1653814216454400000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

See A179420 for a description of the fascinating properties of the e.g.f. A(x) that satisfies: A(A(x)) = x*A'(x).

LINKS

Paul D. Hanna, Table of n, a(n) for n = 1..150

FORMULA

A221019(n)/A221020(n) = A179420(n)/n!.

EXAMPLE

E.g.f. A(x) of A179420 begins:

A(x) = x + 2*x^2/2! + 12*x^3/3! + 132*x^4/4! + 2200*x^5/5! +...+ A179420(n)/n!*x^n +...

or, equivalently,

A(x) = x + 1/1*x^2 + 2/1*x^3 + 11/2*x^4 + 55/3*x^5 + 419/6*x^6 + 1471/5*x^7 + 483673/360*x^8 + 2756471/420*x^9 + 1902667/56*x^10 +...+ A221019(n)/A221020(n)*x^n +...

which satisfies: A(A(x)) = x*A'(x) where:

A'(x) = 1 + 2*x + 12*x^2/2! + 132*x^3/3! + 2200*x^4/4! +...

A(A(x)) = x + 4*x^2/2! + 36*x^3/3! + 528*x^4/4! + 11000*x^5/5! +...

PROG

(PARI) {A179420(n)=local(A=x+x^2+sum(m=3, n-1, A179420(m)*x^m/m!)+x*O(x^n)); if(n<3, n!*polcoeff(A, n),

n!*polcoeff(subst(A, x, A), n)/(n-2))}

{a(n)=denominator(A179420(n)/n!)}

for(n=1, 25, print1(a(n), ", "))

CROSSREFS

Cf. A221019, A179420.

Sequence in context: A276087 A341837 A084678 * A333304 A248896 A102402

Adjacent sequences:  A221017 A221018 A221019 * A221021 A221022 A221023

KEYWORD

nonn,frac

AUTHOR

Paul D. Hanna, Dec 28 2012

STATUS

approved

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Last modified December 8 11:03 EST 2021. Contains 349594 sequences. (Running on oeis4.)