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 A072355 #14 May 10 2019 17:55:02 %S A072355 2,4,22,63,4202,4246,444886,1161238,9362914,26996486,545614671, %T A072355 1640386293,2242930954,2243031802,2243065418,2243115842,18000691527 %N A072355 Numbers k such that sigma(k) = (Pi^2)*(k/6) rounded off (where 0.5 is rounded to 0). %C A072355 In 1838 Dirichlet showed that the average value of sigma(n) is (Pi^2)*(n/6) for large n (see Tattersall). %D A072355 Tattersall, J. "Elementary Number Theory in Nine Chapters", Cambridge University Press, 1999. %e A072355 sigma(444886) = 731808 = (Pi^2 * 444886)/6 rounded off; so 444886 is a term of the sequence. %t A072355 Select[Range[10^6], Round[(Pi^2 * #)/6] == DivisorSigma[1, # ] &] %Y A072355 Cf. A013661 (Pi^2/6), A074920. %K A072355 nonn,more %O A072355 1,1 %A A072355 _Joseph L. Pe_, Jul 18 2002 %E A072355 More terms from _Robert G. Wilson v_, Jul 27 2002 %E A072355 a(10)-a(17) from _Giovanni Resta_, Apr 03 2017