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 A345049 #4 Jun 07 2021 06:50:52 %S A345049 -1,0,-2,3,-12,10,-30,11,2,20,-90,40,-132,30,16,31,-240,48,-306,104,0, %T A345049 50,-462,112,-36,60,26,192,-756,344,-870,79,-80,80,-240,158,-1260,90, %U A345049 -144,312,-1560,636,-1722,440,216,110,-2070,280,-162,152,-320,600,-2652,186,-880,600,-432,140,-3306,1120,-3540,150,348,191 %N A345049 a(n) = A173557(n) * A345001(n). %F A345049 a(n) = A173557(n) * A345001(n). %F A345049 a(n) = A345048(n) - A345050(n). %o A345049 (PARI) %o A345049 A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1])); %o A345049 A173557(n) = factorback(apply(p -> p-1,factor(n)[,1])); %o A345049 A345001(n) = (sigma(n)+A003415(n)-(2*n)); %o A345049 A345049(n) = (A173557(n) * A345001(n)); %Y A345049 Cf. A173557, A345001, A345048, A345050, A345051. %K A345049 sign %O A345049 1,3 %A A345049 _Antti Karttunen_, Jun 06 2021