A076359 - OEIS

%I #20 Oct 18 2018 20:53:54

%S 1,1,1,1,4,4,8,8,8,8,16,16,192,192,192,192,3072,3072,55296,55296,

%T 55296,55296,110592,110592,110592,110592,110592,110592,442368,442368,

%U 13271040,13271040,13271040,13271040,13271040,13271040,477757440

%N a(n) = denominator(n!/phi(n!)).

%C Numerator of Product_{p<=n, p prime} (1 - 1/p). - _Franz Vrabec_, Jan 28 2014

%H Robert Israel, <a href="/A076359/b076359.txt">Table of n, a(n) for n = 1..2926</a>

%F a(n) = denominator(A000142(n)/A048855(n)).

%F a(n) = A038110(A036234(n)). - _Robert Israel_, Oct 18 2018

%p P:= 1: p:= 1:  v:= 1:

%p while p < 100 do q:= nextprime(p);

%p    for i from p to q-1 do A[i]:= v od;

%p    P:= P * (1-1/q);

%p    v:= numer(P);

%p    p:= q;

%p od:

%p seq(A[i],i=1..q-1); # _Robert Israel_, Oct 18 2018

%t dnf[n_]:=With[{nn=n!},Denominator[nn/EulerPhi[nn]]]; Array[dnf,40] (* _Harvey P. Dale_, Feb 21 2015 *)

%o (PARI) a(n) = numerator(prod(p=1, n, if (isprime(p),(1-1/p), 1))); \\ _Michel Marcus_, Jan 28 2014

%Y Cf. A000005, A000142, A036234, A038110, A048855, A076358.

%K easy,nonn,frac

%O 1,5

%A _Labos Elemer_, Oct 08 2002