A163092 Number of reduced words of length n in Coxeter group on 16 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 16, 240, 3600, 53880, 806400, 12069120, 180633600, 2703470280, 40461750000, 605574696720, 9063392310000, 135648138214680, 2030190989349600, 30385049935084320, 454760790684530400, 6806221388012959080, 101865971146974325200, 1524586916316221551920

Offset: 0

Author

John Cannon and N. J. A. Sloane, Dec 03 2009

Keywords

• nonn

Comments

The initial terms coincide with those of A170735, although the two sequences are eventually different.

Computed with MAGMA using commands similar to those used to compute A154638.

Links

• Index entries for linear recurrences with constant coefficients, signature (14,14,14,-105).

Programs

Mathematica

CoefficientList[ Series[(t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(105*t^4 - 14*t^3 - 14*t^2 - 14*t + 1), {t, 0, 16}], t] (* Jean-François Alcover, Nov 26 2013 *)

PARI

Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(105*t^4 - 14*t^3 - 14*t^2 - 14*t + 1) + O(t^20)) \\ Jinyuan Wang, Mar 23 2020

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(105*t^4 - 14*t^3 - 14*t^2 - 14*t + 1).

Extensions

More terms from Jinyuan Wang, Mar 23 2020