A067195 - OEIS

%I #16 Mar 18 2017 19:21:05

%S 1,2,4,30,33,38,42,45,47,48,57,59,60,64,66,69,77,82,85,104,106,118,

%T 121,194,196,201,285,287,288,290,465,467,468,470,499,500,510,610,614,

%U 626,628,631,632,642,718,723,724,785,793,798,811,812,814,823,824,825,838

%N Numbers n such that M(n) = Sum_{i=1..n} mu(sigma(i)) where M(n) is the Mertens function A002321(n).

%H Indranil Ghosh, <a href="/A067195/b067195.txt">Table of n, a(n) for n = 1..263</a> (terms < 5000)

%t M[n_] := Sum[MoebiusMu[k], {k, n}]; Select[Range@ 838, Sum[MoebiusMu[DivisorSigma[1, i]], {i, #}] == M[#] &] (* _Indranil Ghosh_, Mar 16 2017 *)

%o (PARI) isok(n) = sum(i = 1, n, moebius(sigma(i))) == mertens(n); \\ _Michel Marcus_, Sep 24 2013

%Y Cf. A000203, A008683.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Feb 19 2002