A285021 Denominator of binomial(2*n,n)/20^n.

1, 10, 200, 400, 16000, 800000, 16000000, 160000000, 2560000000, 25600000000, 2560000000000, 25600000000000, 1024000000000000, 409600000000000, 8192000000000000, 409600000000000000, 65536000000000000000, 655360000000000000000, 2621440000000000000000, 26214400000000000000000, 5242880000000000000000000, 52428800000000000000000000

Offset

0,2

Links

Chai Wah Wu, Table of n, a(n) for n = 0..769

Formula

A285020(n)/a(n) = (-1/5)^n*sqrt(Pi)/(Gamma(1/2 - n)*Gamma(1 + n)).

Sum_{k>=0} A285020(k)/a(k) = sqrt(5)/2.

Sum_{k>=0} (-1)^k*A285020(k)/a(k) = sqrt(5/6).

Sum_{k>=0} (-1)^(k+1)*A285020(k)/a(k) = -sqrt(5/6).

Mathematica

Denominator[Table[(-1/5)^n*Sqrt[Pi]/(Gamma[1/2-n]*Gamma[1+n]), {n, 0, 25}]]

Crossrefs

Cf. A285020 (numerators).

Sequence in context: A211419 A001085 A079436 * A354410 A126431 A335649

Adjacent sequences: A285018 A285019 A285020 * A285022 A285023 A285024

Keyword

nonn,frac

Author

Ralf Steiner, Apr 08 2017

Status

approved