A071707 - OEIS

%I #11 Aug 20 2021 22:06:39

%S 1,2,6,12,18,24,28,40,84,120,224,234,240,252,360,468,496,672,864,936,

%T 1638,1920,2016,2480,3276,4320,4680,6048,6528,6552,7440,8128,9360,

%U 10880,22320,22932,26208,30240,32640,32760,47616,56896,58752,65520,74880,79360,84480

%N Numbers k that divide tau(k)*sigma(k).

%H Donovan Johnson, <a href="/A071707/b071707.txt">Table of n, a(n) for n = 1..300</a>

%e The divisors of 18 are {1,2,3,6,9,18}, so tau(18)=6 and sigma(18)=1+2+3+6+9+18=39, 18 is a term as 18*13=6*39=tau(18)*sigma(18).

%Y Cf. A007691, A064840(n)=A000005(n)*A000203(n).

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jun 03 2002