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 A168831 #12 Nov 24 2016 18:31:08
%S A168831 1,10,90,810,7290,65610,590490,5314410,47829690,430467210,3874204890,
%T A168831 34867844010,313810596090,2824295364810,25418658283290,
%U A168831 228767924549610,2058911320946490,18530201888518410,166771816996665690
%N A168831 Number of reduced words of length n in Coxeter group on 10 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.
%C A168831 The initial terms coincide with those of A003952, although the two sequences are eventually different.
%C A168831 First disagreement at index 20: a(20) = 13508517176729920845, A003952(20) = 13508517176729920890. - _Klaus Brockhaus_, Apr 01 2011
%C A168831 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168831 G. C. Greubel, <a href="/A168831/b168831.txt">Table of n, a(n) for n = 0..1000</a>
%H A168831 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, -36).
%F A168831 G.f.: (t^20 + 2*t^19 + 2*t^18 + 2*t^17 + 2*t^16 + 2*t^15 + 2*t^14 + 2*t^13 + 2*t^12 + 2*t^11 + 2*t^10 + 2*t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(36*t^20 - 8*t^19 - 8*t^18 - 8*t^17 - 8*t^16 - 8*t^15 - 8*t^14 - 8*t^13 - 8*t^12 - 8*t^11 - 8*t^10 - 8*t^9 - 8*t^8 - 8*t^7 - 8*t^6 - 8*t^5 - 8*t^4 - 8*t^3 - 8*t^2 - 8*t + 1).
%t A168831 CoefficientList[Series[(t^20 + 2*t^19 + 2*t^18 + 2*t^17 + 2*t^16 + 2*t^15 + 2*t^14 + 2*t^13 + 2*t^12 + 2*t^11 + 2*t^10 + 2*t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(36*t^20 - 8*t^19 - 8*t^18 - 8*t^17 - 8*t^16 - 8*t^15 - 8*t^14 - 8*t^13 - 8*t^12 - 8*t^11 - 8*t^10 - 8*t^9 - 8*t^8 - 8*t^7 - 8*t^6 - 8*t^5 - 8*t^4 - 8*t^3 - 8*t^2 - 8*t + 1), {t,0,100}], t] (* _G. C. Greubel_, Nov 22 2016 *)
%Y A168831 Cf. A003952 (G.f.: (1+x)/(1-9*x)).
%K A168831 nonn
%O A168831 0,2
%A A168831 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009