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 A005018 #19 Jan 27 2018 18:19:42 %S A005018 1,2,4,5,10,20 %N A005018 Divisors of 20: a finite sequence associated with the Lie algebra A_4. %D A005018 E. B. Dynkin, Semisimple subalgebras of semisimple Lie algebras, Am. Math. Soc. Translations, Series 2, Vol. 6, 1957, pp. 111-244, esp. p. 211. %H A005018 <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a> %F A005018 a(n) = A161706(n-1). - _Reinhard Zumkeller_, Jun 21 2009 %o A005018 (Sage) divisors(20); # _Zerinvary Lajos_, Jun 13 2009 %o A005018 (PARI) divisors(20) %K A005018 nonn,fini,full,easy %O A005018 1,2 %A A005018 _N. J. A. Sloane_