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A229257 O.g.f.: Sum_{n>=0} x^n / Product_{k=1..n} (1 - n^2*k*x). 5
1, 1, 2, 14, 168, 3147, 90563, 3561231, 185790622, 12599020184, 1071164190670, 111813313594259, 14140296360430353, 2132273568722682621, 378197030144360862958, 78127192632748956075174, 18627308660113953164384812, 5081218748742336002185874439, 1574128413278644602881499193579 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

FORMULA

a(n) = Sum_{k=0..n} (k^2)^(n-k) * Stirling2(n, k).

E.g.f.: Sum_{n>=0} (exp(n^2*x) - 1)^n / (n! * n^(2*n)).

EXAMPLE

O.g.f.: A(x) = 1 + x + 2*x^2 + 14*x^3 + 168*x^4 + 3147*x^5 + 90563*x^6 +...

where

A(x) = 1 + x/(1-x) + x^2/((1-2^2*1*x)*(1-2^2*2*x)) + x^3/((1-3^2*1*x)*(1-3^2*2*x)*(1-3^2*3*x)) + x^4/((1-4^2*1*x)*(1-4^2*2*x)*(1-4^2*3*x)*(1-4^2*4*x)) +...

Exponential Generating Function.

E.g.f.: E(x) = 1 + x + 2*x^2/2! + 14*x^3/3! + 168*x^4/4! + 3147*x^5/5! +...

where

E(x) = 1 + (exp(x)-1) + (exp(4*x)-1)^2/(2!*4^2) + (exp(9*x)-1)^3/(3!*9^3) + (exp(16*x)-1)^4/(4!*16^4) + (exp(25*x)-1)^5/(5!*25^5) +...

MATHEMATICA

Flatten[{1, Table[Sum[(k^2)^(n-k) * StirlingS2[n, k], {k, 0, n}], {n, 1, 20}]}] (* Vaclav Kotesovec, May 08 2014 *)

PROG

(PARI) {a(n)=polcoeff(sum(m=0, n, x^m/prod(k=1, m, 1-m^2*k*x +x*O(x^n))), n)}

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

(PARI) {a(n)=n!*polcoeff(sum(m=0, n, (exp(m^2*x+x*O(x^n))-1)^m/(m!*m^(2*m))), n)}

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

(PARI) {Stirling2(n, k)=n!*polcoeff(((exp(x+x*O(x^n))-1)^k)/k!, n)}

{a(n)=sum(k=0, n, (k^2)^(n-k) * Stirling2(n, k))}

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

CROSSREFS

Cf. A229258, A229259, A229260, A229261; A229233, A229234, A220181, A122399.

Sequence in context: A277373 A084946 A047055 * A188194 A046247 A141012

Adjacent sequences:  A229254 A229255 A229256 * A229258 A229259 A229260

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Sep 17 2013

STATUS

approved

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Last modified July 28 14:19 EDT 2021. Contains 346335 sequences. (Running on oeis4.)