A279288 - OEIS

%I #17 Sep 08 2022 08:46:18

%S 1,2,1,3,1,2,1,1,1,1,1,3,1,2,1,5,1,1,1,3,1,2,1,1,3,1,2,1,1,1,1,3,1,1,

%T 1,3,1,2,1,1,1,2,1,3,1,2,1,5,1,3,1,1,1,4,1,1,1,1,1,3,1,2,1,7,1,2,1,3,

%U 1,1,1,1,1,1,3,1,1,1,1,5,5,1,1,1,1,2,1

%N a(n) = denominator of (phi(n)/tau(n)).

%C a(n) = denominator of (A000010(n)/A000005(n)).

%C See A279287 (numerator of (phi(n)/tau(n))) and A063070 (phi(n)-tau(n)).

%C a(n) = 1 and A279287(n) = 1 for numbers n in A020488; A279287(n) > a(n) for numbers n in A279289.

%H Jaroslav Krizek, <a href="/A279288/b279288.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = 1 for numbers in A020491.

%e For n = 6: phi(6)/tau(6) = 2/4 = 1/2; a(6) = 2.

%t Table[Denominator[EulerPhi[n]/DivisorSigma[0, n]], {n, 120}] (* _Michael De Vlieger_, Dec 10 2016 *)

%o (Magma) [Denominator(EulerPhi(n)/NumberOfDivisors(n)): n in[1..1000]]

%o (PARI) a(n) = denominator(eulerphi(n)/numdiv(n)) \\ _Felix Fröhlich_, Dec 09 2016

%Y Cf. A000005, A000010, A020488, A020490, A020491, A063070, A279287, A279289.

%K nonn,frac

%O 1,2

%A _Jaroslav Krizek_, Dec 09 2016