A113837 - OEIS

%I #15 Nov 14 2024 08:23:45

%S 5,7,11,13,14,15,17,19,22,23,26,27,29,31,33,34,35,37,38,39,41,43,46,

%T 47,51,53,54,55,56,57,58,59,61,62,65,67,69,71,73,74,77,78,79,82,83,85,

%U 86,87,88,89,91,92,93,94,95,97,101,102,103,104,106,107,109,110,111,113,114

%N 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.

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

%p 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

%t okQ[n_] := DivisorSigma[0, DivisorSigma[1, n]] >

%t            DivisorSigma[1, DivisorSigma[0, n]];

%t Select[Range[120], okQ] (* _Jean-François Alcover_, Nov 14 2024 *)

%Y Cf. A062068, A062069.

%K nonn

%O 1,1

%A _Leroy Quet_, Jan 23 2006

%E More terms from _Emeric Deutsch_, Feb 06 2006