A343217 Numbers k such that A003415(sigma(k)) >= k.

3, 5, 6, 7, 8, 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, 41, 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

Offset

1,1

Links

Table of n, a(n) for n=1..82.

Index entries for sequences related to sigma(n)

Mathematica

Select[Range[100], If[#2 < 2, 0, #2 Total[#2/#1 & @@@ FactorInteger[#2]]] >= #1 & @@ {#, DivisorSigma[1, #]} &] (* Michael De Vlieger, Apr 08 2021 *)

Prog

(PARI)
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
isA343217(n) = (A003415(sigma(n))>=n);

Crossrefs

Cf. A000203, A003415.

Cf. A343216 (complement), A343218 (subsequence).

Sequence in context: A138891 A163162 A181744 * A160685 A080218 A080651

Adjacent sequences: A343214 A343215 A343216 * A343218 A343219 A343220

Keyword

nonn

Author

Antti Karttunen, Apr 08 2021

Status

approved