A113837 A number k is included if d(sigma(k)) > sigma(d(k)), where d(k) is number of positive divisors of k and sigma(k) is sum of positive divisors of k.

5, 7, 11, 13, 14, 15, 17, 19, 22, 23, 26, 27, 29, 31, 33, 34, 35, 37, 38, 39, 41, 43, 46, 47, 51, 53, 54, 55, 56, 57, 58, 59, 61, 62, 65, 67, 69, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 97, 101, 102, 103, 104, 106, 107, 109, 110, 111, 113, 114

Offset

1,1

Links

Table of n, a(n) for n=1..67.

Example

d(sigma(14)) = d(24) = 8, and sigma(d(14)) = sigma(4) = 7. Since 8 > 7, 14 is in the sequence.

Maple

with(numtheory): a:=proc(n) if tau(sigma(n))>sigma(tau(n)) then n else fi end: seq(a(n), n=1..122); # Emeric Deutsch, Feb 06 2006

Mathematica

okQ[n_] := DivisorSigma[0, DivisorSigma[1, n]] >
           DivisorSigma[1, DivisorSigma[0, n]];
Select[Range[120], okQ] (* Jean-François Alcover, Nov 14 2024 *)

Crossrefs

Cf. A062068, A062069.

Sequence in context: A082684 A096379 A098761 * A255363 A245757 A240912

Adjacent sequences: A113834 A113835 A113836 * A113838 A113839 A113840

Keyword

nonn

Author

Leroy Quet, Jan 23 2006

Extensions

More terms from Emeric Deutsch, Feb 06 2006

Status

approved