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A178345

a(n) = 2^A006218(n)/( (n!)^2*Sum_{m=0..n} 1/(m!*(2*n-m+1)!) ).

1, 3, 15, 70, 630, 2772, 48048, 205920, 3500640, 29560960, 496624128, 2076791808, 138452787200, 575111577600, 9530420428800, 157569617756160, 5199797385953280, 21410930412748800, 1408363422705254400, 5781702472158412800, 379279682173591879680, 6212962412748362219520

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..21.

FORMULA

a(n) = 2^A006218(n)/( Sum_{m=0..n} Beta(n+1,n-m+1)*binomial(n,m) ), where Beta(x,y) = Gamma(x)*Gamma(y)/Gamma(x+y).

MAPLE

A006218 := proc(n) add( floor(n/i), i=1..n) ; end proc:

A178345 := proc(n) n!^2*add( 1/(2*n-m+1)!/m!, m=0..n) ; 2^A006218(n)/% ; end proc:

seq(A178345(n), n=0..10) ;

MATHEMATICA