A102408 - OEIS

%I #10 Jan 08 2018 01:58:28

%S 1,5,6,8,9,11,10,15,15,14,17,24,24,21,13,19,27,25,29,26,44,44,29,46,

%T 39,46,27,42,47,47,54,35,41,60,51,37,48,45,49,50,49,53,77,86,86,51,96,

%U 75,70,80,99,110,81,84,102,82,96,114,53,108,115,105,116,91

%N Harmonic means associated with A090945.

%C A perfect number N=2^(p-1)*M(p) (=A000396), {with associated Mersenne prime M(p)=2^p -1 (=A000668)}, has harmonic mean N*tau(N)/sigma(N) = p (=A000043).

%F a(n)= m*tau(m)/sigma(m), where m=A090945(n), tau=A000005 and sigma=A000203

%o (PARI) lista(nn) = {for (n=1, nn, ab = sigma(n)/n; hm = numdiv(n)/ab; if ((type(hm) == "t_INT") && (ab != 2), print1(hm, ", ")););} \\ _Michel Marcus_, Oct 26 2013

%K nonn

%O 1,2

%A _Lekraj Beedassy_, Jan 07 2005

%E a(1)=1 as well as a(29)=47 inserted and more terms added by _Michel Marcus_, Oct 26 2013