A220353 G.f.: Sum_{n>=0} (1 - (1-x)^n)^n.

1, 1, 4, 23, 176, 1697, 19805, 271669, 4285195, 76430799, 1521161530, 33422603485, 803584699252, 20986514811397, 591616582807036, 17905570068475471, 579092313210791549, 19931241131544637637, 727395001560116046739, 28057672464546863483509, 1140566596105346550309751, 48735378037084078566334897, 2183719157723179429519093520, 102386962560815561519635957007

Offset

0,3

Comments

Limit n->infinity A220353(n)/A187826(n) = 1. - Vaclav Kotesovec, Nov 08 2014

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..300

Formula

G.f.: Sum_{n>=1} (1-x)^n * (1 - (1-x)^n)^(n-1).

a(n) = c * n! / (sqrt(n) * (log(2))^(2*n)), where c = 0.93418651575946259471737... . - Vaclav Kotesovec, May 06 2014

In closed form, c = 2^(log(2)/2-1) / (log(2) * sqrt(Pi*(1-log(2)))). - Vaclav Kotesovec, May 03 2015

Example

G.f.: A(x) = 1 + x + 4*x^2 + 23*x^3 + 176*x^4 + 1697*x^5 + 19805*x^6 +...
where the g.f. satisfies the identities:
(1) A(x) = 1 + x + (2*x - x^2)^2 + (3*x - 3*x^2 + x^3)^3 + (4*x - 6*x^2 + 4*x^3 - x^4)^4 + (5*x - 10*x^2 + 10*x^3 - 5*x^4 + x^5)^5 +...
(2) A(x) = (1-x) + (1-x)^2*(2*x - x^2) + (1-x)^3*(3*x - 3*x^2 + x^3)^2 + (1-x)^4*(4*x - 6*x^2 + 4*x^3 - x^4)^3 + (1-x)^5*(5*x - 10*x^2 + 10*x^3 - 5*x^4 + x^5)^4 +...

Mathematica

terms = 24;
gf = 1 + Sum[(1 - (1 - x)^n)^n, {n, 1, terms}] + O[x]^terms;
CoefficientList[gf, x] (* Jean-François Alcover, Jul 01 2018 *)

Prog

(PARI) {a(n)=local(q=1/(1-x+x*O(x^n)), A=1); A=sum(k=0, n, q^(-k^2)*(q^k-1)^k); polcoeff(A, n)}
for(n=0, 30, print1(a(n), ", "))
(PARI) {a(n)=local(q=1/(1-x+x*O(x^n)), A=1); A=sum(k=1, n+1, q^(-k^2)*(q^k-1)^(k-1)); polcoeff(A, n)}
for(n=0, 30, print1(a(n), ", "))

Crossrefs

Cf. A220352, A122400, A187827, A187826.

Sequence in context: A350669 A067545 A004041 * A089465 A220214 A106174

Adjacent sequences: A220350 A220351 A220352 * A220354 A220355 A220356

Keyword

nonn

Author

Paul D. Hanna, Dec 11 2012

Extensions

a(22)-a(23) corrected by Andrew Howroyd, Feb 22 2018

Status

approved