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A187755 E.g.f.: Sum_{n>=0} (1 - exp(-n^2*x))^n. 5
1, 1, 31, 3991, 1340251, 929043391, 1153715889691, 2333670966674671, 7180487882511523051, 31919495229412870788031, 196909477461357591810377851, 1632140626754602443266222263951, 17701927686793740884448652685728651, 245721757633690118910277310669218472671 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..13.

FORMULA

O.g.f.: Sum_{n>=0} n^(2*n) * n! * x^n / Product_{k=1..n} (1 + n^2*k*x).

a(n) = Sum_{k=0..n} (-1)^(n-k) * k^(2*n) * k! * Stirling2(n,k).

a(n) == 1 (mod 10) for n>=0.

a(n) == 31 (mod 60) for n>=2.

a(n) ~ c * d^n * (n!)^3 / n, where d = 6.8312860494079582446988970296645779575650627187418208311407895492635... and c = 0.192038502554748256318271067254582378566365276592... . - Vaclav Kotesovec, May 08 2014

EXAMPLE

O.g.f.: F(x) = 1 + x + 31*x^2 + 3991*x^3 + 1340251*x^4 + 929043391*x^5 +...

where

F(x) = 1 + x/(1+x) + 2^4*2!*x^2/((1+2^2*1*x)*(1+2^2*2*x)) + 3^6*3!*x^3/((1+3^2*1*x)*(1+3^2*2*x)*(1+3^2*3*x)) + 4^8*4!*x^4/((1+4^2*1*x)*(1+4^2*2*x)*(1+4^2*3*x)*(1+4^2*4*x)) +...

...

E.g.f.: A(x) = 1 + x + 31*x^2/2! + 3991*x^3/3! + 1340251*x^4/4! +...

where

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

MATHEMATICA

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

PROG

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

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

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

for(n=0, 20, 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, (-1)^(n-k)*k^(2*n)*k!*Stirling2(n, k))}

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

CROSSREFS

Cf. A220181, A203798, A229260.

Sequence in context: A001237 A289397 A177465 * A115736 A110848 A214109

Adjacent sequences:  A187752 A187753 A187754 * A187756 A187757 A187758

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jan 03 2013

STATUS

approved

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Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)