A343219 - OEIS

%I #12 Apr 09 2021 08:47:36

%S 0,0,1,0,0,1,1,0,0,1,1,1,0,1,1,0,1,0,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,

%T 1,0,0,1,1,1,0,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,1,1,1,0,1,1,0,1,1,1,1,

%U 1,1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,0,0,1,1,1,1

%N a(n) = 1 if A003415(sigma(k)) > k, otherwise 0.

%H Antti Karttunen, <a href="/A343219/b343219.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%t Array[Boole[If[#2 < 2, 0, #2 Total[#2/#1 & @@@ FactorInteger[#2]]] > #1] & @@ {#, DivisorSigma[1, #]} &, 105] (* _Michael De Vlieger_, Apr 08 2021 *)

%o (PARI)

%o A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

%o A343219(n) = (A003415(sigma(n))>n);

%Y Cf. A000203, A003415, A343220, A343225.

%Y Characteristic function of A343218.

%K nonn

%O 1

%A _Antti Karttunen_, Apr 08 2021