A108775 - OEIS

%I #17 Sep 18 2015 08:19:17

%S 1,1,1,1,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,1,1,

%T 1,2,1,1,1,2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,1,1,2,1,1,

%U 1,2,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,1,1,1,2,1,1,1,2,1,2,1,2,1

%N a(n) = floor(sigma(n)/n).

%C The sequence is unbounded. - Vrabec

%C First occurrence of k: 1,6,120,27720,..., which is A023199. - _Robert G. Wilson v_, Jun 28 2005

%C a(n) > 1 if n is perfect or abundant. a(n) = 2 if n is perfect or primitive abundant (see A091191). - _Alonso del Arte_, Feb 06 2012

%D W. Sierpinski, Elementary Theory of Numbers, 1987, p. 174 ff.

%H Reinhard Zumkeller, <a href="/A108775/b108775.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = floor(A017665(n)/A017666(n)). - _Michel Marcus_, Sep 18 2015

%e a(6) = 2 because sigma(6)/6 = (1 + 2 + 3 + 6)/6 = 2.

%t Table[ Floor[ DivisorSigma[1, n]/n], {n, 105}] (* _Robert G. Wilson v_, Jun 28 2005 *)

%o (Haskell)

%o a108775 n = div (a000203 n) n  -- _Reinhard Zumkeller_, Mar 23 2013

%o (PARI) a(n) = sigma(n)\n; \\ _Michel Marcus_, Sep 18 2015

%Y Cf. A000203, A054024.

%Y Cf. A017665, A017666.

%K nonn

%O 1,6

%A _Franz Vrabec_, Jun 27 2005

%E More terms from _Robert G. Wilson v_, Jun 28 2005