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A244821 E.g.f.: Sum_{n>=0} exp(n*3^n*x) * x^n/n!. 4
1, 1, 7, 82, 2377, 125956, 13786849, 2767780450, 1068587690545, 755247058160104, 990216775791709921, 2368086973433913986398, 10296184143094869761471305, 81305381330548263178299374860, 1153396004725120797831718629888193, 29585981132637810261211357828811890786 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Robert Israel, Table of n, a(n) for n = 0..86

Vaclav Kotesovec, Asymptotic of sequences A244820, A244821 and A244822

FORMULA

O.g.f.: Sum_{n>=0} x^n/(1 - n*3^n*x)^(n+1).

a(n) = Sum_{k=0..n} C(n,k) * k^(n-k) * 3^(k*(n-k)).

EXAMPLE

E.g.f.: A(x) = 1 + x + 7*x^2/2! + 82*x^3/3! + 2377*x^4/4! + 125956*x^5/5! +...

where

A(x) = 1 + exp(3*x)*x + exp(3^2*x)^2*x^2/2! + exp(3^3*x)^3*x^3/3! + exp(3^4*x)^4*x^4/4! + exp(3^5*x)^5*x^5/5! + exp(3^6*x)^6*x^6/6! +...

MAPLE

N:= 31:

S:= series(add(exp(n*3^n*x)*x^n/n!, n=0..N), x, N):

seq(coeff(S, x, j)*j!, j=0..N-1); # Robert Israel, Jul 04 2017

MATHEMATICA

Flatten[{1, Table[Sum[Binomial[n, k]*k^(n-k)*3^(k*(n-k)), {k, 0, n}], {n, 1, 20}]}] (* Vaclav Kotesovec, Jul 11 2014 *)

PROG

(PARI) a(n) = sum(k=0, n, binomial(n, k) * k^(n-k) * 3^(k*(n-k)) )

for(n=0, 25, print1(a(n), ", "))

(PARI) a(n)=n!*polcoeff(sum(k=0, n, exp(k*3^k*x +x*O(x^n))*x^k/k!), n)

for(n=0, 25, print1(a(n), ", "))

(PARI) a(n)=polcoeff(sum(k=0, n, x^k/(1-k*3^k*x +x*O(x^n))^(k+1)), n)

for(n=0, 25, print1(a(n), ", "))

CROSSREFS

Cf. A244820, A244822, A245076.

Sequence in context: A268653 A242375 A333984 * A304591 A139951 A141872

Adjacent sequences: A244818 A244819 A244820 * A244822 A244823 A244824

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 06 2014

STATUS

approved

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Last modified January 29 00:02 EST 2023. Contains 359905 sequences. (Running on oeis4.)