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%I #26 Apr 09 2018 13:00:40
%S 1,6,12,2,20,24,28,120,3,180,66,60,78,1260,360,4,102,108,152,120,126,
%T 132,184,144,5,936,5040,1120,232,210,248,240,9240,2040,1680,6,370,342,
%U 312,300,410,336,430,330,360,414,470,360,7,420,25704,196560,636,3780
%N Square root of b_1*b_2*...*b_t corresponding to smallest values of t in R. L. Graham's sequence (A006255).
%C a(n) = A000196(A245530(n)). - _Reinhard Zumkeller_, Jul 25 2014
%D R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 147.
%H Peter Kagey, <a href="/A066401/b066401.txt">Table of n, a(n) for n = 1..1000</a> (First 125 terms from Reinhard Zumkeller)
%H R. L. Graham, <a href="http://www.jstor.org/stable/2689569">Bijection between integers and composites</a>, Problem 1242, Math. Mag., 60 (1987), p. 180.
%e a(2) = 6 because the best such sequence is 2,3,6 for which the product is 36 = 6^2.
%t Table[k = 0; While[Length@ # == 0 &@ Set[f, Select[Rest@ Subsets@ Range@ k, IntegerQ@ Sqrt[n (Times @@ # &[n + #])] &]], k++]; If[IntegerQ@ Sqrt@ n, k = {n}, k = n + Prepend[First@ f, 0]]; Sqrt[Times @@ k], {n, 22}] (* _Michael De Vlieger_, Oct 26 2016 *)
%o (Haskell)
%o a066401 = a000196 . a245530 -- _Reinhard Zumkeller_, Jul 25 2014
%Y Cf. A000196, A006255, A066400, A245499, A245530.
%K nonn,easy
%O 1,2
%A _N. J. A. Sloane_, Dec 25 2001
%E More terms from Larry Reeves (larryr(AT)acm.org), Jan 06 2005
%E More terms from _Joshua Zucker_, May 18 2006
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