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

Author

Leroy Quet, Jan 23 2006

Keywords

• nonn

Examples

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

Crossrefs

Cf. A062068, A062069.

Programs

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 *)

Extensions

More terms from Emeric Deutsch, Feb 06 2006