A163055 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 12, 132, 1452, 15906, 174240, 1908720, 20908800, 229042770, 2509019700, 27484733100, 301077971700, 3298119892650, 36128829891000, 395768617233000, 4335396381723000, 47491541694374250, 520239981289297500

Offset

0,2

Comments

The initial terms coincide with those of A003954, although the two sequences are eventually different.

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

Links

Table of n, a(n) for n=0..17.

Index entries for linear recurrences with constant coefficients, signature (10, 10, 10, -55).

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(55*t^4 - 10*t^3 - 10*t^2 - 10*t + 1)

Mathematica

coxG[{4, 55, -10}] (* The coxG program is at A169452 *) (* Harvey P. Dale, Jul 03 2020 *)

Crossrefs

Sequence in context: A097826 A010580 A010577 * A163432 A163957 A063813

Adjacent sequences: A163052 A163053 A163054 * A163056 A163057 A163058

Keyword

nonn

Author

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

Status

approved