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 A169212 #12 Jul 23 2021 10:26:15
%S A169212 1,7,42,252,1512,9072,54432,326592,1959552,11757312,70543872,
%T A169212 423263232,2539579392,15237476352,91424858112,548549148672,
%U A169212 3291294892032,19747769352192,118486616113152,710919696678912,4265518180073472
%N A169212 Number of reduced words of length n in Coxeter group on 7 generators S_i with relations (S_i)^2 = (S_i S_j)^28 = I.
%C A169212 The initial terms coincide with those of A003949, although the two sequences are eventually different.
%C A169212 First disagreement at index 28: a(28) = 7164432583542284746731, A003949(28) = 7164432583542284746752. - _Klaus Brockhaus_, May 24 2011
%C A169212 Computed with Magma using commands similar to those used to compute A154638.
%H A169212 <a href="/index/Rec#order_28">Index entries for linear recurrences with constant coefficients</a>, signature (5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, -15).
%F A169212 G.f.: (t^28 + 2*t^27 + 2*t^26 + 2*t^25 + 2*t^24 + 2*t^23 + 2*t^22 + 2*t^21 + 2*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)/(15*t^28 - 5*t^27 - 5*t^26 - 5*t^25 - 5*t^24 - 5*t^23 - 5*t^22 - 5*t^21 - 5*t^20 - 5*t^19 - 5*t^18 - 5*t^17 - 5*t^16 - 5*t^15 - 5*t^14 - 5*t^13 - 5*t^12 - 5*t^11 - 5*t^10 - 5*t^9 - 5*t^8 - 5*t^7 - 5*t^6 - 5*t^5 - 5*t^4 - 5*t^3 - 5*t^2 - 5*t + 1).
%t A169212 coxG[{28,15,-5}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Jul 23 2021 *)
%Y A169212 Cf. A003949 (G.f.: (1+x)/(1-6*x)).
%K A169212 nonn
%O A169212 0,2
%A A169212 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009