A057022 - OEIS

%I #28 Dec 25 2016 02:14:41

%S 1,1,2,2,3,3,4,3,4,4,6,4,7,6,6,6,9,6,10,7,8,9,12,7,10,10,10,9,15,9,16,

%T 10,12,13,12,10,19,15,14,11,21,12,22,14,13,18,24,12,19,15,18,16,27,15,

%U 18,15,20,22,30,14,31,24,17,18,21,18,34,21,24,18

%N a(n) = floor((sum of divisors of n) / (number of divisors of n)), or floor(sigma_1(n)/sigma_0(n)).

%C Floor of mean of divisors of n. - _Jon E. Schoenfield_, Dec 24 2016

%H Reinhard Zumkeller, <a href="/A057022/b057022.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = (A000203(n) - A054025(n))/A000005(n).

%e a(4)=2 since the 3 divisors of 4 are 1, 2 and 4 and floor((1 + 2 + 4)/3) = floor(7/3) = 2.

%t Floor[Table[Total[Divisors[n]]/Length[Divisors[n]],{n,20}]] (* _Daniel Jolly_, Nov 15 2014 *)

%t Table[Floor[DivisorSigma[1,n]/DivisorSigma[0,n]],{n,70}] (* _Harvey P. Dale_, Jan 14 2015 *)

%o (Haskell)

%o a057022 n = a000203 n `div` a000005 n

%o -- _Reinhard Zumkeller_, Jan 06 2012

%o (PARI) a(n) = sigma(n)\numdiv(n); \\ _Michel Marcus_, Nov 15 2014

%Y Cf. A000005, A000203, A009205, A054025, A057020, A057021.

%Y Cf. A003601.

%K nonn

%O 1,3

%A _Henry Bottomley_, Jul 21 2000