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 A066401 Square root of b_1*b_2*...*b_t corresponding to smallest values of t in R. L. Graham's sequence (A006255). 5
 1, 6, 12, 2, 20, 24, 28, 120, 3, 180, 66, 60, 78, 1260, 360, 4, 102, 108, 152, 120, 126, 132, 184, 144, 5, 936, 5040, 1120, 232, 210, 248, 240, 9240, 2040, 1680, 6, 370, 342, 312, 300, 410, 336, 430, 330, 360, 414, 470, 360, 7, 420, 25704, 196560, 636, 3780 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = A000196(A245530(n)). - Reinhard Zumkeller, Jul 25 2014 REFERENCES R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 147. LINKS Peter Kagey, Table of n, a(n) for n = 1..1000 (First 125 terms from Reinhard Zumkeller) R. L. Graham, Bijection between integers and composites, Problem 1242, Math. Mag., 60 (1987), p. 180. EXAMPLE a(2) = 6 because the best such sequence is 2,3,6 for which the product is 36 = 6^2. MATHEMATICA 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 *) PROG (Haskell) a066401 = a000196 . a245530  -- Reinhard Zumkeller, Jul 25 2014 CROSSREFS Cf. A000196, A006255, A066400, A245499, A245530. Sequence in context: A242931 A110645 A064913 * A263538 A076590 A113660 Adjacent sequences:  A066398 A066399 A066400 * A066402 A066403 A066404 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Dec 25 2001 EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), Jan 06 2005 More terms from Joshua Zucker, May 18 2006 STATUS approved

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Last modified October 16 16:13 EDT 2019. Contains 328101 sequences. (Running on oeis4.)