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A118023 Column 0 of triangle A118022, where the matrix square of A118022 shifts each column up 1 row, dropping the main diagonal of powers of 2. 1
1, 1, 3, 19, 243, 6227, 319251, 32737427, 6714170259, 2754046149011, 2259333156408723, 3706972573115098515, 12164337831474297132435, 79833941280970262512121235, 1047892334589811621056371520915 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Numerators of the q-Catalan numbers for q = 1/2. - John Keith, Feb 19 2021

LINKS

Table of n, a(n) for n=0..14.

FORMULA

G.f.: 1 = Sum_{n>=0} a(n)*x^n*prod_{k=0, n} (1-2^k*x) with a(0)=1.

a(n) = 2^(n*(n-1)/2)*b(n) where b(0)=1 and b(n)=sum(i=0,n-1,b(i)*b(n-1-i)/2^i). - Benoit Cloitre, Oct 25 2006

G.f.: Sum_{n>=0} a(n)*x^n/2^(n*(n+1)/2) = 1/(1 - (x/2)/(1 - (x/2^2)/(1 - (x/2^3)/(1 - (x/2^4)/(1 - (x/2^5)/(1 - ...)))))), a continued fraction. - Paul D. Hanna, Sep 28 2012

EXAMPLE

1 = (1-x) + 1*x*(1-x)*(1-2*x) + 3*x^2*(1-x)*(1-2*x)*(1-4*x) + 19*x^3*(1-x)*(1-2*x)*(1-4*x)*(1-8*x) + 243*x^4*(1-x)*(1-2*x)*(1-4*x)*(1-8*x)*(1-16*x) + ...

PROG

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

{a(n)=local(CF=1+x*O(x^n)); for(k=1, n, CF=1/(1-x/2^(n-k+1)*CF)); 2^(n*(n+1)/2)*polcoeff(CF, n)} - Paul D. Hanna, Sep 28 2012

CROSSREFS

Cf. A118022.

Sequence in context: A157675 A135754 A340225 * A054590 A261495 A069344

Adjacent sequences:  A118020 A118021 A118022 * A118024 A118025 A118026

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Apr 10 2006

STATUS

approved

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Last modified May 16 03:53 EDT 2022. Contains 353688 sequences. (Running on oeis4.)