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A068553 a(n) = lcm(1,2,...,2n) / (n*binomial(2n, n)). 6
1, 1, 1, 3, 2, 5, 15, 7, 28, 126, 30, 165, 198, 143, 1001, 15015, 3640, 884, 7956, 1938, 19380, 203490, 49742, 572033, 980628, 240350, 3124550, 766935, 188370, 2731365, 40970475, 20160075, 4962480, 81880920, 20173560, 353037300 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Known to be always an integer.

LINKS

Robert Israel, Table of n, a(n) for n = 1..3774

Hojoo Lee, Re: LCM [1,2,..,N] > 2^{N-1}, NMBRTHRY Mailing List, Feb 18 2002.

FORMULA

a(n) = A068550(n)/n.

a(n) = A048619(2*n-1).

MAPLE

Num:= 2: Den:=2: Res:= 1:

for n from 2 to 100 do

  Num:= ilcm(Num, 2*n-1, 2*n);

  Den:= Den*(4+2/(n-1));

  Res:= Res, Num/Den;

od:

Res; # Robert Israel, Dec 26 2018

MATHEMATICA

Table[(LCM@@Range[2n])/(n Binomial[2n, n]), {n, 40}] (* Harvey P. Dale, Jul 17 2012 *)

CROSSREFS

Bisection of A048619.

Sequence in context: A092935 A137455 A111273 * A174909 A187943 A301493

Adjacent sequences:  A068550 A068551 A068552 * A068554 A068555 A068556

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Mar 23 2002

STATUS

approved

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Last modified December 9 22:27 EST 2019. Contains 329880 sequences. (Running on oeis4.)