This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A244576 #20 Mar 22 2024 04:23:29 %S A244576 0,0,2,7,23,38,69,89,133,227,268,397,483,536,632,821,1018,1125,1355, %T A244576 1511,1633,1890,2077,2406,2906,3150,3263,3509,3680,3960,5026,5319, %U A244576 5854,6003,6909,7130,7761,8345,8681,9381,9986,10351,11456,11771,12212,12481,14128 %N A244576 Sum of all proper divisors of all positive integers <= prime(n). %C A244576 Also sum of all proper divisors of all positive integers <= prime(n)-1. %C A244576 Also zero together with the numbers that are repeated in A244049. %F A244576 a(n) = A244049(A000040(n)-1) = A244049(A000040(n)). %F A244576 a(n) ~ (Pi^2/12 - 1/2) * n^2 * log(n)^2. - _Amiram Eldar_, Mar 22 2024 %o A244576 (PARI) a(n) = sum(i=2, prime(n), sigma(i)-i-1); \\ _Michel Marcus_, Sep 29 2014 %Y A244576 Cf. A000040, A000203, A048050, A244049, A244578, A244583. %K A244576 nonn %O A244576 1,3 %A A244576 _Omar E. Pol_, Jun 30 2014 %E A244576 More terms from _Michel Marcus_, Sep 29 2014