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 A072504 a(n) = LCM of divisors of n which are <= sqrt(n). 5

%I

%S 1,1,1,2,1,2,1,2,3,2,1,6,1,2,3,4,1,6,1,4,3,2,1,12,5,2,3,4,1,30,1,4,3,

%T 2,5,12,1,2,3,20,1,6,1,4,15,2,1,12,7,10,3,4,1,6,5,28,3,2,1,60,1,2,21,

%U 8,5,6,1,4,3,70,1,24,1,2,15,4,7,6,1,40,9,2,1,84,5,2,3,8,1,90,7,4,3,2,5,24

%N a(n) = LCM of divisors of n which are <= sqrt(n).

%H Reinhard Zumkeller, <a href="/A072504/b072504.txt">Table of n, a(n) for n = 1..10000</a>

%e a(20) = 4: the divisors of 20 are 1,2,4,5,10 and 20; a(20) = lcm(1,2,4) = 4.

%p A072504 := proc(n)

%p local ds ;

%p ds := [] ;

%p for d in numtheory[divisors](n) do

%p if d^2 <= n then

%p ds := [op(ds),d] ;

%p end if;

%p end do:

%p ilcm(op(ds)) ;

%p end proc:

%p seq(A072504(n),n=1..20) ; # _R. J. Mathar_, Oct 03 2014

%t Table[LCM@@Select[Divisors[n],#<=Sqrt[n]&],{n,100}] (* _Harvey P. Dale_, Aug 26 2014 *)

%o a072504 = foldl1 lcm . a161906_row -- _Reinhard Zumkeller_, Mar 08 2013

%Y Cf. A072505.

%Y Cf. A161906, A072499.

%K nonn

%O 1,4

%A _Amarnath Murthy_, Jul 20 2002

%E More terms from _Matthew Conroy_, Sep 09 2002

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Last modified June 23 22:56 EDT 2021. Contains 345402 sequences. (Running on oeis4.)