A069166 - OEIS

%I #22 Feb 19 2021 04:24:54

%S 1,6,14,40,120,244,280,440,494,680,920,1220,2040,2840,2968,3480,6360,

%T 9880,10680,16376,20618,25160,32280,34720,40136,40280,42136,45560,

%U 45994,46280,85880,91160,120408,200680,213280,231080,242840,377080,410552,412360,421480,441496,447320

%N Numbers k such that k*Sum_{d|k} 1/sigma(d) is an integer.

%H Amiram Eldar, <a href="/A069166/b069166.txt">Table of n, a(n) for n = 1..300</a>

%t Select[Range[125000],IntegerQ[# Total[1/DivisorSigma[1,Divisors[#]]]]&] (* _Harvey P. Dale_, Nov 03 2017 *)

%o (PARI) isok(k) = denominator(k*sumdiv(k, d, 1/sigma(d))) == 1; \\ _Michel Marcus_, Feb 15 2021

%Y Cf. A069164.

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Apr 09 2002

%E More terms from _Michel Marcus_, Feb 15 2021