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A317337 O.g.f. A(x) satisfies: [x^n] exp( n^3*x*A(x) ) * (n+1 - n*A(x)) = 0 for n>=1. 4
1, 1, 12, 729, 111440, 31377625, 14001201036, 9064452341847, 8027821828474816, 9322437359885669613, 13746212321035446900300, 25094943743950232692612534, 55574014665416527079564569056, 146797467684802516650481763597455, 456012687037844090869850529901126900, 1645914373011657806464530612985244787000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Compare: the factorial series F(x) = Sum_{n>=0} n!*x^n satisfies

(1) [x^n] exp( n^2*x*F(x) ) * (n + 1 - n*F(x)) = 0 for n>=1,

(2) [x^n] exp( n^3*x*F(x) ) * (n^2 + 1 - n^2*F(x)) = 0 for n>=1.

It is remarkable that this sequence should consist entirely of integers.

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..300

FORMULA

a(n) ~ sqrt(1-c) * 3^(3*n) * n^(2*n - 3/2) / (sqrt(2*Pi) * c^n * (3-c)^(2*n) * exp(2*n)), where c = -LambertW(-3*exp(-3)) = 0.1785606278779211065968086697... = -A226750. - Vaclav Kotesovec, Aug 06 2018

EXAMPLE

O.g.f.: A(x) = 1 + x + 12*x^2 + 729*x^3 + 111440*x^4 + 31377625*x^5 + 14001201036*x^6 + 9064452341847*x^7 + 8027821828474816*x^8 + ...

ILLUSTRATION OF DEFINITION.

The table of coefficients of x^k/k! in exp( n^3*x*A(x) ) * (n+1 - n*A(x)) begins:

n=1: [1, 0, -23, -4376, -2674995, -3765464504, ...];

n=2: [1, 6, 0, -8908, -5494464, -7640806512, ...];

n=3: [1, 24, 549, 0, -8632395, -12056269968, ...];

n=4: [1, 60, 3616, 204712, 0, -17114998496, -45010750350080, ...];

n=5: [1, 120, 14505, 1750880, 197597325, 0, -60559334101475, ...];

n=6: [1, 210, 44352, 9406044, 1987128000, 391935493296, 0, ...]; ...

in which the coefficients of x^n in row n form a diagonal of zeros.

PROG

(PARI) {a(n) = my(A=[1], m); for(i=1, n, A=concat(A, 0); m=#A; A[m] = Vec( exp( (m-1)^3*x*(Ser(A)) ) * (m - (m-1)*Ser(A)) )[m]/(m-1) ); A[n+1]}

for(n=0, 20, print1(a(n), ", "))

CROSSREFS

Cf. A305110, A305114, A305115, A305116, A317338.

Sequence in context: A042749 A219568 A202792 * A089036 A273033 A276636

Adjacent sequences:  A317334 A317335 A317336 * A317338 A317339 A317340

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Aug 01 2018

STATUS

approved

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Last modified September 29 05:48 EDT 2020. Contains 337425 sequences. (Running on oeis4.)