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A245110 G.f.: Sum_{n>=0} ( exp(-1/(1-n*x)) / (1-n*x)^n ) / n!. 4
1, 1, 4, 23, 161, 1302, 11810, 117889, 1277890, 14894043, 185226966, 2442933979, 33998594943, 497207012018, 7613797641286, 121711037138949, 2025687745708717, 35020194893837462, 627586143525936866, 11636932722633705392, 222893347544826491780, 4403534468187986689781 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Compare the g.f. to:  Sum_{n>=0} exp(-(1+n*x)) * (1+n*x)^n / n! = 1/(1-x).

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..150

FORMULA

a(n) = Sum_{k=1..n} Stirling2(n, k) * C(n+k-1, k-1) for n>0 with a(0)=1.

Row sums of Triangle A245111.

EXAMPLE

G.f.: A(x) = 1 + x + 4*x^2 + 23*x^3 + 161*x^4 + 1302*x^5 + 11810*x^6 +...

where

A(x) = exp(-1) + exp(-1/(1-x))/(1-x) + (exp(-1/(1-2*x))/(1-2*x)^2)/2!

+ (exp(-1/(1-3*x))/(1-3*x)^3)/3! + (exp(-1/(1-4*x))/(1-4*x)^4)/4!

+ (exp(-1/(1-5*x))/(1-5*x)^5)/5! + (exp(-1/(1-6*x))/(1-6*x)^6)/6!

+ (exp(-1/(1-7*x))/(1-7*x)^7)/7! + (exp(-1/(1-8*x))/(1-8*x)^8)/8! +...

simplifies to a power series in x with integer coefficients.

PROG

(PARI) /* From definition (requires setting suitable precision) */ \p100

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

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

(PARI) /* From a(n) = Sum_{k=1..n} Stirling2(n, k) * C(n+k-1, k-1) */

{Stirling2(n, k) = sum(j=0, k, (-1)^(k+j) * binomial(k, j) * j^n) / k!}

{a(n)=if(n==0, 1, sum(k=1, n, Stirling2(n, k) * binomial(n+k-1, k-1)))}

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

(PARI) /* As row sums of triangle A245111: */

{A245111(n, k)=local(A=1+x*y); A=sum(k=0, n, 1/(1-k*x+x*O(x^n))^k*y^k/k!*exp(-y/(1-k*x+x*O(x^n))+y*O(y^n))); polcoeff(polcoeff(A, n, x), k, y)}

{a(n) = sum(k=0, n, A245111(n, k))}

/* Print Initial Rows of Triangle A245111: */

{for(n=0, 10, for(k=0, n, print1(A245111(n, k), ", ")); print(""))}

/* Row Sums yield A245110: */

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

CROSSREFS

Cf. A245109, A245111.

Sequence in context: A198916 A182969 A263186 * A342988 A304074 A307402

Adjacent sequences:  A245107 A245108 A245109 * A245111 A245112 A245113

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 12 2014

STATUS

approved

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Last modified November 28 10:05 EST 2021. Contains 349401 sequences. (Running on oeis4.)