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 A378099 #13 Dec 01 2024 11:37:17 %S A378099 2,21,321,7721,184729,185145,21110729,54929017,134099385,3331670169 %N A378099 The smallest number whose sum of proper divisors (aliquot parts) is the repunit number (10^n - 1)/9, denoted by R_n. %e A378099 a(4) = 7721 because 7721 is the smallest number whose sum of proper divisors is R_4 = 1111. %o A378099 (PARI) a(n) = my(k=1); while (sigma(k)-k != (10^n - 1)/9, k++); k; \\ _Michel Marcus_, Nov 16 2024 %Y A378099 Cf. A001065, A002275. %K A378099 nonn,hard,more %O A378099 1,1 %A A378099 _Shyam Sunder Gupta_, Nov 16 2024