A163110 Number of reduced words of length n in Coxeter group on 19 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 19, 342, 6156, 110637, 1988388, 35735751, 642249324, 11542621410, 207446086881, 3728258709552, 67004941956759, 1204224973728534, 21642549713419572, 388963830112221249, 6990528525469894908, 125635046969043641691, 2257935858412484688900, 40580032910411799982386

Offset: 0

Author

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

Keywords

• nonn

Comments

The initial terms coincide with those of A170738, 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 (17,17,17,-153).

Programs

Mathematica

coxG[{4,153,-17}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Aug 24 2019 *)

PARI

Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(153*t^4 - 17*t^3 - 17*t^2 - 17*t + 1) + O(t^20)) \\ Jinyuan Wang, Mar 23 2020

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(153*t^4 - 17*t^3 - 17*t^2 - 17*t + 1).

Extensions

More terms from Jinyuan Wang, Mar 23 2020