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 A060795 Write product of first n primes as x*y with x
 1, 2, 5, 14, 42, 165, 714, 3094, 14858, 79534, 447051, 2714690, 17395070, 114371070, 783152070, 5708587335, 43848093003, 342444658094, 2803119896185, 23619540863730, 201813981102615, 1793779293633437, 16342050964565645, 154170926013430326, 1518409177581024365 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Or, lower central divisor of n-th primorial. Subsequence of A005117 (squarefree numbers). - Michel Marcus, Feb 22 2016 LINKS Amiram Eldar, Table of n, a(n) for n = 1..33 FORMULA a(n) = A060775(A002110(n)). - Labos Elemer, Apr 27 2001 EXAMPLE n=8: q(8)=2*3*5*7*11*13*17*19=9699690. Its 128th and 129th divisors are {3094,3135}: a(8)=3094 and 3094 < A000196(9699690)=3114<3135. [Corrected by Colin Barker, Oct 22 2010] 2*3*5*7 = 210 = 14*15 with difference of 1, so a(4) = 14. MAPLE F:= proc(n) local P, N, M;      P:= {seq(ithprime(i), i=1..n)};      N:= floor(sqrt(convert(P, `*`)));      M:= map(convert, combinat:-powerset(P), `*`);      max(select(`<=`, M, N)) end proc: map(F, [\$1..20]); # Robert Israel, Feb 22 2016 MATHEMATICA a[n_] := (m = Times @@ Prime[Range[n]] ; dd = Divisors[m]; dd[[Length[dd]/2 // Floor]]); Table[Print[an = a[n]]; an, {n, 1, 25}] (* Jean-François Alcover, Oct 15 2016 *) PROG a(n) = my(m=prod(i=1, n, prime(i))); divisors(m)[numdiv(m)\2]; \\ Michel Marcus, Feb 22 2016 CROSSREFS Cf. A061055, A061056, A061057, A061058, A061059, A061060, A061030, A061031, A061032, A061033, A060755, A000196, A033677. Sequence in context: A047046 A063545 A061058 * A071743 A071747 A071751 Adjacent sequences:  A060792 A060793 A060794 * A060796 A060797 A060798 KEYWORD nonn AUTHOR Labos Elemer, Apr 27 2001 EXTENSIONS More terms from Ed Pegg Jr, May 28 2001 Terms 16 through 23 computed by Jud McCranie, Apr 15 2000 a(24) and a(25) from Robert Israel, Feb 22 2016 a(25) corrected by Jean-François Alcover, Oct 15 2016 STATUS approved

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Last modified April 13 06:02 EDT 2021. Contains 342935 sequences. (Running on oeis4.)