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 A161439 #13 Mar 21 2025 17:09:49
%S A161439 1,7,27,76,174,343,602,961,1415,1940,2493,3017,3450,3736,3836,3736,
%T A161439 3450,3017,2493,1940,1415,961,602,343,174,76,27,7,1
%N A161439 Number of reduced words of length n in the Weyl group A_7.
%C A161439 Computed with MAGMA using commands similar to those used to compute A161409.
%D A161439 N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)
%D A161439 J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.
%F A161439 G.f. for A_m is the polynomial Product_{k=1..m} (1-x^(k+1))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A008302.
%Y A161439 Row n=8 of A008302.
%K A161439 nonn,fini,full
%O A161439 0,2
%A A161439 _John Cannon_ and _N. J. A. Sloane_, Nov 30 2009