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 A286884 #27 Jul 22 2021 23:48:08 %S A286884 108927,448335,544635,53781261243,92526188391,612887145325 %N A286884 Odd numbers k such that the set of distinct prime divisors of k is equal to the set of distinct prime divisors of the sum of proper divisors of k. %C A286884 The first four terms that are divisible by 108927 are 108927, 544635, 92526188391, 4094089374375. %C A286884 a(7) > 10^12. 2981095241355 is also a term. - _Giovanni Resta_, Aug 03 2017 %e A286884 92526188391 is a term because sigma(92526188391) - 92526188391 = 3^2*7*13^3*19*181^2 and 92526188391 = 3^2*7^2*13^2*19^3*181. %t A286884 fQ[n_] := Transpose[ FactorInteger[ n]][[1]] == Transpose[ FactorInteger[ DivisorSigma[1, n] - n]][[1]]; (* _Robert G. Wilson v_, Aug 02 2017 *) %o A286884 (PARI) a001065(n) = if(n==0, 0, sigma(n) - n) %o A286884 a027748(n) = factor(n)[, 1]~ %o A286884 is(n) = n%2==1 && a027748(n)==a027748(a001065(n)) \\ _Felix Fröhlich_, Aug 02 2017 %o A286884 (PARI) list(lim)=my(v=List(),f,t,o); forfactored(n=108927,lim\1, f=n[2]; if(f[1,1]==2, next); t=sigma(f)-n[1]; for(i=1,#f~, o=valuation(t,f[i,1]); if(o==0, next(2)); t/=f[i,1]^o); if(t==1, listput(v,n[1]))); Vec(v) \\ _Charles R Greathouse IV_, Aug 02 2017 %Y A286884 Cf. A001065, A007947, A027598, A027748, A286876. %K A286884 nonn,more %O A286884 1,1 %A A286884 _Altug Alkan_, Aug 02 2017 %E A286884 a(4)-a(6) from _Giovanni Resta_, Aug 03 2017