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A134805

Denominator of Sum_{i=1..n} 1/(i^2*binomial(2*i,i)).

1, 2, 24, 360, 2016, 16800, 237600, 151351200, 605404800, 30875644800, 53330659200, 6453009763200, 11416863427200, 1929449919196800, 1929449919196800, 93256746094512000, 680225677395264000, 196585220767231296000, 93119315100267456000, 1243794691794272409792000

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OFFSET

0,2

COMMENTS

For this sum times 2/3 see A130549/A130550 with offset 1.

LINKS

Table of n, a(n) for n=0..19.

C. Elsner, On recurrence formulas for sums involving binomial coefficients, Fib. Q., 43,1 (2005), 31-45.

FORMULA

Sum_{i >= 1} 1/(i^2*binomial(2*i, i)) = Pi^2/18.

EXAMPLE

0, 1/2, 13/24, 197/360, 1105/2016, 9211/16800, 130277/237600, 82987349/151351200, ...