A053569 - OEIS

%I #14 Jun 15 2024 05:48:39

%S 3,6,13,18,12,31,18,20,32,36,24,31,42,40,30,48,54,48,38,42,44,78,72,

%T 48,57,93,72,98,54,72,90,60,62,127,84,144,68,96,144,72,74,124,140,96,

%U 80,121,126,84,108,132,120,180,90,168,144,120,98,156,217,102,104,192,162

%N Sum of divisors of numbers which cannot be sum of divisors of any number.

%C See also comments in A053474.

%H Amiram Eldar, <a href="/A053569/b053569.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000203(A007369(n)).

%e The 13th non-sigma number is 26. Its divisors are {26,13,2,1} of which the sum is 42. So a(13) = 42.

%e Also a(20) = 42, the divisor sum of 20th term in A007369, which is 41.

%Y Cf. A000203, A007369, A053474.

%K nonn

%O 1,1

%A _Labos Elemer_, Jan 17 2000