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Floor((Product of composite numbers up to n)/(product of primes up to n)).
1

%I #14 Nov 03 2016 09:54:01

%S 1,0,0,0,0,0,0,0,8,82,7,89,6,96,1450,23201,1364,24565,1292,25858,

%T 543035,11946780,519425,12466205,311655142,8103033711,218781910200,

%U 6125893485615,211237706400,6337131192016,204423586839,6541554778855

%N Floor((Product of composite numbers up to n)/(product of primes up to n)).

%C Note 1 is neither prime nor composite.

%H Harvey P. Dale, <a href="/A073699/b073699.txt">Table of n, a(n) for n = 1..644</a>

%e a(10) = Floor((4*6*8*9*10)/(2*3*5*7)) = 82.

%p a := 1:b := 1:for i from 2 to 100 do if isprime(i) then a := a*i: else b := b*i:fi: c[i] := floor(b/a):od:c[1] := 1:seq(c[j],j=1..100);

%t Table[t1 = Select[x = Range[n], PrimeQ]; Floor[Divide @@ Times @@@ {Complement[x, t1], t1}], {n, 32}] (* _Jayanta Basu_, Jul 06 2013 *)

%t Module[{upto=40,pr,cm},pr=Prime[Range[PrimePi[upto]]];cm=Select[ Range[ upto], CompositeQ]; Table[ Floor[Times@@Select[cm,#<=n&]/ Times@@ Select[ pr,#<=n&]],{n,upto}]] (* _Harvey P. Dale_, Nov 03 2016 *)

%K nonn

%O 1,9

%A _Amarnath Murthy_, Aug 12 2002

%E More terms from _Sascha Kurz_, Aug 15 2002