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%I #13 Oct 23 2013 12:53:55
%S 3,20,210,504,0,51480,180180,4084080,0,21162960,0,2059318800,0,0,
%T 36100888223400,8494326640800,0,281206918792800,0,0,0,
%U 409547311252279200,0,619808900849199341280,0,54749786241679275146400,0,5663770990518545704800,0
%N Smallest number divisible by all numbers from 1 to 2*n-1, but not divisible by n, or 0 if impossible.
%C a(n) = 0 if and only if n has more than one distinct prime in its prime factorization (i.e., if and only if n is a member of A024619).
%e a(4) = 210 because 210 is divisible by 1,2,3,5,6,7 but not 4. a(6) is 0 because there's no number divisible by 1,2,3,4,5,7,8,9,10,11 but not 6 (any number divisible by both 2 and 3 is divisible by 6).
%p with(numtheory): A230478 := proc (n) if 1 < nops(factorset(n)) then return 0: end if: return lcm($1..(n-1), $(n+1)..(2*n-1)): end proc: seq(A230478(n), n=2..35); # _Nathaniel Johnston_, Oct 22 2013
%K nonn,easy
%O 2,1
%A _J. Lowell_, Oct 20 2013
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