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 A091575 #7 Jan 30 2018 18:57:36 %S A091575 8,14,20,26,32,38,44,48,52,56,60,62,64,64,64,64,64,62,60,56,52,48,44, %T A091575 38,32,26,20,14,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A091575 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A091575 Poincaré series [or Poincare series] of the preprojective algebra of a Dynkin diagram of type E_8. %D A091575 I. Reiten, Dynkin diagrams and the representation theory of algebras, Notices of the AMS, Vol. 44, Number 5. %e A091575 The series is a polynomial because the algebra is finite dimensional. For an arbitrary Dynkin diagram the corresponding polynomial is (n+n*x^h-2*x^e_1-...-2*x^e_n)/(1-x)^2, where n is the rank, h the Coxeter number and e_1,...,e_n the Coxeter exponents of the associated Coxeter group. %Y A091575 Cf. A089010, A091571, A091572, A091573, A091574, A091576, A091577. %K A091575 easy,nonn %O A091575 0,1 %A A091575 _Paul Boddington_, Jan 22 2004