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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 A290159 A083562

Adjacent sequences:  A196526 A196527 A196528 * A196530 A196531 A196532

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 03 2011

STATUS

approved

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Last modified April 18 14:35 EDT 2019. Contains 322209 sequences. (Running on oeis4.)