A163174 Number of reduced words of length n in Coxeter group on 24 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

1, 24, 552, 12696, 291732, 6703488, 154034496, 3539441664, 81330144060, 1868823662376, 42942280730712, 986738081076264, 22673505553878564, 520997277758500752, 11971601073631152624, 275086336118245407888

Offset

0,2

Comments

The initial terms coincide with those of A170743, 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..15.

Index entries for linear recurrences with constant coefficients, signature (22,22,22,-253).

Formula

G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(253*t^4 - 22*t^3 - 22*t^2 - 22*t + 1).

Mathematica

CoefficientList[Series[(t^4 + 2 t^3 + 2 t^2 + 2 t + 1)/(253 t^4 - 22 t^3 - 22 t^2 - 22 t + 1), {t, 0, 20}], t] (* Jinyuan Wang, Mar 23 2020 *)

Crossrefs

Sequence in context: A010561 A334673 A342888 * A163519 A163992 A164637

Adjacent sequences: A163171 A163172 A163173 * A163175 A163176 A163177

Keyword

nonn

Author

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

Status

approved