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 A076765 Partial sums of Chebyshev sequence S(n,8)=U(n,4)=A001090(n+1). 13
 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 M. Margenstern, Number of polyhedra at distance n in {5,3,4} 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(S(k, 8), k=0..n) 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. a(n) = -1/6+(7/12)*(4-sqrt(15))^n-(3/20)*(4-sqrt(15))^n*sqrt(15)+(7/12)*(4+sqrt(15))^n+(3/20) *sqrt(15)*(4+sqrt(15))^n. - Paolo P. Lava, Jun 25 2008 MATHEMATICA Join[{a=1, b=9}, Table[c=8*b-a+1; a=b; b=c, {n, 60}]] (*From Vladimir Joseph Stephan Orlovsky, Jan 19 2011*) CROSSREFS Cf. A092521 (partial sums of S(n, 7)). Cf. A212336 for more sequences with g.f. of the type 1/(1-k*x+k*x^2-x^3). Sequence in context: A045993 A084327 A057085 * A006634 A129328 A162960 Adjacent sequences:  A076762 A076763 A076764 * A076766 A076767 A076768 KEYWORD nice,easy,nonn AUTHOR Maurice MARGENSTERN (margens(AT)lita.univ-metz.fr), Nov 14 2002 EXTENSIONS Extension and Chebyshev comments from Wolfdieter Lang, Aug 31 2004 STATUS approved

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