%I #19 Jan 27 2018 18:19:42
%S 1,2,4,5,10,20
%N Divisors of 20: a finite sequence associated with the Lie algebra A_4.
%D 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 <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>
%F a(n) = A161706(n-1). - _Reinhard Zumkeller_, Jun 21 2009
%o (Sage) divisors(20); # _Zerinvary Lajos_, Jun 13 2009
%o (PARI) divisors(20)
%K nonn,fini,full,easy
%O 1,2
%A _N. J. A. Sloane_