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 A257533 #8 Mar 15 2022 14:46:09 %S A257533 2,5,3,7,9,8,10,13,5,15,14,19,12,21,16,25,7,20,16,22,31,33,18,26,39, %T A257533 18,43,22,45,32,20,34,49,24,55,40,28,61,24,11,63,44,46,26,69,50,73,24, %U A257533 34,75,36,81,56,30,85,13,62,91,64,42,28,99,70 %N A257533 Sum of the proper divisors of the n-th semiprime. %C A257533 For purposes of this sequence, the proper divisors of a number include all divisors other than 1 and the number itself. - _Harvey P. Dale_, Mar 15 2022 %H A257533 Charles R Greathouse IV, <a href="/A257533/b257533.txt">Table of n, a(n) for n = 1..10000</a> %F A257533 a(n) = A048050(A001358(n)). %F A257533 A083681(n)-a(n) = A088707(n). %p A257533 seq(A048050(A001358(n)),n=1..80) ; %t A257533 Total[Rest[Most[Divisors[#]]]]&/@Select[Range[250],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Mar 15 2022 *) %o A257533 (PARI) go(lim)=my(v=List()); forprime(p=2,lim\2, forprime(q=2,min(lim\p,p), listput(v,[p*q,if(q<p,p+q,p)]))); v=vecsort(Vec(v),1); apply(u->u[2],v) \\ _Charles R Greathouse IV_, Apr 28 2015 %Y A257533 Cf. A083681. %K A257533 nonn,easy %O A257533 1,1 %A A257533 _R. J. Mathar_, Apr 28 2015