A343218 Numbers k such that A003415(sigma(k)) > k.

3, 6, 7, 10, 11, 12, 14, 15, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 38, 39, 40, 42, 43, 44, 45, 46, 47, 48, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 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

Offset: 1

Author

Antti Karttunen, Apr 08 2021

Keywords

• nonn

Links

• Index entries for sequences related to sigma(n)

Crossrefs

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

Programs

Mathematica

Select[Range[103], If[#2 < 2, 0, #2 Total[#2/#1 & @@@ FactorInteger[#2]]] > #1 & @@ {#, DivisorSigma[1, #]} &] (* Michael De Vlieger, Apr 08 2021 *)

PARI

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
isA343218(n) = (A003415(sigma(n))>n);