A076765 - OEIS

A076765

Partial sums of Chebyshev sequence S(n,8) = U(n,4) = A001090(n+1).

1, 9, 72, 568, 4473, 35217, 277264, 2182896, 17185905, 135304345, 1065248856, 8386686504, 66028243177, 519839258913, 4092685828128, 32221647366112, 253680493100769, 1997222297440041, 15724097886419560, 123795560793916440

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

In the tiling {5,3,4} of 3-dimensional hyperbolic space, the number of regular dodecahedra with right angles of the n generation which are contained in an eighth of space (intersection of three pairwise perpendicular hyperplanes which are supported by the faces of a dodecahedron at a vertex).

Let beta be the greatest real root of the polynomial which is defined by the above recurrent equation. Consider the representation of positive numbers in the basis beta. Then the language which consists of the maximal representations of positive numbers is neither regular nor context-free (M. Margenstern's theorem, see second reference, above).

REFERENCES

M. Margenstern and G. Skordev, Tools for devising cellular automata in the 3-dimensional hyperbolic space, I - the geometrical part, proceedings of SCI'2002, Orlando, Florida, Jul 14-18, (2002), vol. XI, 542-547 Vol. 100 (1993), pp. 1-25.

M. Margenstern and G. Skordev, Tools for devising cellular automata in the 3-dimensional hyperbolic space, II - the numeric algorithms, proceedings of SCI'2002, Orlando, Florida, Jul 14-18, (2002), vol. XI, 548-552

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

M. Margenstern, Number of polyhedra at distance n in {5,3,4}

Index entries for sequences related to Chebyshev polynomials.

Index entries for linear recurrences with constant coefficients, signature (9,-9,1).

FORMULA

a(n+3) = 9*a(n+2) - 9*a(n+1) + a(n); initial values: a(0) = 1, a(1) = 9, a(2) = 72

a(n) = Sum_{k=0..n} S(k, 8) with S(k, x) = U(k, x/2) Chebyshev's polynomials of the second kind.

G.f.: 1/((1-x)*(1 - 8*x + x^2)) = 1/(1 - 9*x + 9*x^2 - x^3).

a(n) = 8*a(n-1) - a(n-2) + 1; a(-1)=0, a(0)=1.

a(n) = (S(n+1, 8) - S(n, 8) - 1)/6, n >= 0.

MATHEMATICA