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A218669 O.g.f.: Sum_{n>=0} 1/(1-n^3*x)^n * x^n/n! * exp(-x/(1-n^3*x)). 8
1, 0, 1, 7, 97, 1561, 41136, 1551814, 72440460, 4281320257, 324623105584, 30086950057627, 3299720918091511, 428431079916572044, 65637957066642609845, 11659659637028895337265, 2367270866164121777222596, 546795407830461739380895161, 143176487805296033192642234802 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Compare g.f. to the curious identity:

1/(1-x^2) = Sum_{n>=0} (1+n*x)^n * x^n/n! * exp(-x*(1+n*x)).

LINKS

Table of n, a(n) for n=0..18.

EXAMPLE

O.g.f.: A(x) = 1 + x^2 + 7*x^3 + 97*x^4 + 1561*x^5 + 41136*x^6 +...

where

A(x) = exp(-x) + x/(1-x)*exp(-x/(1-x)) + x^2/(1-8*x)^2/2!*exp(-x/(1-8*x)) + x^3/(1-27*x)^3/3!*exp(-x/(1-27*x)) + x^4/(1-64*x)^4/4!*exp(-x/(1-64*x)) + x^5/(1-125*x)^5/5!*exp(-x/(1-125*x)) +...

simplifies to a power series in x with integer coefficients.

PROG

(PARI) {a(n)=local(A=1+x, X=x+x*O(x^n)); A=sum(k=0, n, 1/(1-k^3*X)^k*x^k/k!*exp(-X/(1-k^3*X))); polcoeff(A, n)}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A218667, A218668, A218670, A217900.

Sequence in context: A243867 A232290 A011943 * A188441 A178808 A083083

Adjacent sequences:  A218666 A218667 A218668 * A218670 A218671 A218672

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Nov 04 2012

STATUS

approved

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Last modified August 18 18:19 EDT 2018. Contains 313834 sequences. (Running on oeis4.)