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A068550 a(n) = lcm{1, ..., 2n} / binomial(2n, n). 4

%I

%S 1,1,2,3,12,10,30,105,56,252,1260,330,1980,2574,2002,15015,240240,

%T 61880,15912,151164,38760,406980,4476780,1144066,13728792,24515700,

%U 6249100,84362850,21474180,5462730,81940950,1270084725,645122400

%N a(n) = lcm{1, ..., 2n} / binomial(2n, n).

%C Known to be always an integer.

%H Hojoo Lee, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=NMBRTHRY;2e3bb004.0202">Re: LCM [1,2,..,N] > 2^{N-1}</a>, NMBRTHRY Mailing List, Feb 18 2002.

%F a(n) = A099996(n) / A000984(n) = A003418(2*n) / A001405(2*n) = A180000(2*n) = A263673(2*n).

%F a(n) = n * A068553(n) = n * A048619(2*n-1).

%Y Bisection of A180000 and A263673.

%K nonn,easy

%O 0,3

%A _N. J. A. Sloane_, Mar 23 2002

%E a(0)=1 prepended by _Max Alekseyev_, Oct 23 2015

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Last modified December 10 23:29 EST 2019. Contains 329910 sequences. (Running on oeis4.)