A343218 - OEIS

%I #7 Apr 08 2021 22:13:18

%S 3,6,7,10,11,12,14,15,17,19,20,21,22,23,24,26,27,28,29,30,31,32,33,34,

%T 35,38,39,40,42,43,44,45,46,47,48,51,52,53,54,55,56,57,58,59,60,62,63,

%U 65,66,67,68,69,70,71,72,74,75,76,77,78,79,80,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,98,99,102,103

%N Numbers k such that A003415(sigma(k)) > k.

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

%t Select[Range[103], If[#2 < 2, 0, #2 Total[#2/#1 & @@@ FactorInteger[#2]]] > #1 & @@ {#, DivisorSigma[1, #]} &] (* _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 isA343218(n) = (A003415(sigma(n))>n);

%Y Cf. A000203, A003415, A343219 (characteristic function).

%K nonn

%O 1,1

%A _Antti Karttunen_, Apr 08 2021