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 A074751 #24 Apr 04 2025 07:03:04 %S A074751 1,4,44,260,1350,6284,6954,13364,273366,333546,466614,4659934050 %N A074751 Numbers k such that the sum of the anti-divisors of k = sum of proper divisors (or aliquot parts) of k. %C A074751 Integers k such that A066417(k) = A001065(k) %C A074751 a(13) > 10^10. - _Hiroaki Yamanouchi_, Mar 18 2015 %o A074751 (PARI) spd(n) = if( n==0, 0, sigma(n) - n); \\ A001065 %o A074751 sad(n) = my(k); if(n>1, k=valuation(n, 2); sigma(2*n+1)+sigma(2*n-1)+sigma(n/2^k)*2^(k+1)-6*n-2, 0); \\ A066417 %o A074751 isok(k) = sad(k) == spd(k); \\ _Michel Marcus_, Mar 30 2025 %Y A074751 Cf. A001065, A066417, A066272. %K A074751 nonn,more %O A074751 1,2 %A A074751 _Jason Earls_, Sep 06 2002 %E A074751 a(12) from _Hiroaki Yamanouchi_, Mar 18 2015