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 A196529 Half of greatest common divisor of products of first n prime numbers and first n composite numbers. 3
 1, 3, 3, 3, 15, 15, 105, 105, 105, 105, 105, 105, 1155, 1155, 1155, 15015, 15015, 15015, 15015, 15015, 15015, 255255, 255255, 255255, 4849845, 4849845, 4849845, 4849845, 4849845, 4849845, 111546435, 111546435, 111546435, 111546435, 111546435, 111546435 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = gcd(A002110(n),A036691(n)) / 2. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..1000 EXAMPLE a(3) = gcd(2*3*5,4*6*8)/2 = gcd(30,192)/2 = 6/2 = 3; a(4) = gcd(2*3*5*7,4*6*8*9)/2 = gcd(210,1728)/2 = 6/2 = 3; a(5) = gcd(2*3*5*7*11,4*6*8*9*10)/2 = gcd(2310,17280)/2 = 30/2 = 15. MATHEMATICA nn=40; With[{prs=Prime[Range[nn]], comps=Take[Complement[Range[Prime[nn]], Prime[ Range[nn]]], nn]}, Rest[Table[GCD[Times@@Take[prs, n], Times@@Take[ comps, n]]/2, {n, nn}]]] (* Harvey P. Dale, Oct 16 2011 *) CROSSREFS Cf. A196527, A070826. Sequence in context: A269347 A183554 A229847 * A110668 A176248 A290159 Adjacent sequences:  A196526 A196527 A196528 * A196530 A196531 A196532 KEYWORD nonn AUTHOR Reinhard Zumkeller, Oct 03 2011 STATUS approved

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Last modified January 21 06:26 EST 2022. Contains 350473 sequences. (Running on oeis4.)