A165174 - OEIS

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A165174

Number of reduced words of length n in Coxeter group on 42 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I.

1, 42, 1722, 70602, 2894682, 118681962, 4865960442, 199504378122, 8179679502141, 335366859552480, 13750041240205200, 563751690789107520, 23113819319921875440, 947666592017104044960, 38854330268613859072080

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OFFSET

0,2

COMMENTS

The initial terms coincide with those of A170761, 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..14.

Index entries for linear recurrences with constant coefficients, signature (40, 40, 40, 40, 40, 40, 40, -820).

FORMULA

G.f. (t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(820*t^8 -

40*t^7 - 40*t^6 - 40*t^5 - 40*t^4 - 40*t^3 - 40*t^2 - 40*t + 1)

CROSSREFS

Sequence in context: A163743 A164112 A164686 * A165693 A166230 A166436

Adjacent sequences: A165171 A165172 A165173 * A165175 A165176 A165177

KEYWORD

nonn

AUTHOR

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

STATUS

approved