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%I #22 Jul 10 2021 03:02:23
%S 1,2,6,12,60,120,840,1680,5040,10080,110880,221760,2882880,5765760,
%T 17297280,34594560,588107520,1176215040,22348085760,44696171520,
%U 134088514560,268177029120,6168071669760,12336143339520,61680716697600
%N a(1) = 1, a(n) = a(n-1) times smallest prime factor of n.
%C a(n) is the product of the smallest divisors > 1 of all the numbers from 2 to n.
%H Reinhard Zumkeller, <a href="/A072486/b072486.txt">Table of n, a(n) for n = 1..1000</a>
%e a(5) = 60. a(6) = 1*2*3*2*5*2 = 120. Also a(6) = a(5) * 2 = 120.
%t a = {1}; Do[AppendTo[a, a[[n - 1]] FactorInteger[n][[1, 1]]], {n, 2, 25}]; a (* _Michael De Vlieger_, Aug 25 2015 *)
%t nxt[{n_,a_}]:={n+1,a*FactorInteger[n+1][[1,1]]}; NestList[nxt,{1,1},30][[All,2]] (* _Harvey P. Dale_, May 03 2018 *)
%o (PARI) al(n)=local(v=vector(n));v[1]=1;for(k=2,n,v[k]=v[k-1]*factor(k)[1,1]);v \\ _Franklin T. Adams-Watters_, Jan 13 2012
%o (PARI) A072486(n)=prod(k=2,n,factor(k)[1,1]) \\ _M. F. Hasler_, Jan 13 2012
%o (Haskell)
%o a072486 n = a072486_list !! (n-1)
%o a072486_list = scanl1 (*) a020639_list
%o -- _Reinhard Zumkeller_, Apr 10 2014
%Y Cf. A020639, A104350.
%K nonn
%O 1,2
%A _Amarnath Murthy_, Jul 13 2002
%E More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 25 2003
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