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A063810
Growth series for Heisenberg group.
0
1, 4, 12, 36, 82, 164, 294, 476, 724, 1052, 1464, 1972, 2590, 3324, 4186, 5188, 6336, 7644, 9124, 10780, 12626, 14676, 16934, 19412, 22124, 25076, 28280, 31748, 35486, 39508, 43826, 48444, 53376, 58636, 64228, 70164, 76458, 83116
OFFSET
0,2
REFERENCES
P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 156.
LINKS
Moon Duchin, Counting in Groups: Fine Asymptotic Geometry, Notices of the AMS 63.8 (2016), pp. 871-974. See p. 873. [There may be a typo for c_8 in the recurrence given there]
Moon Duchin and Michael Shapiro, Rational growth in the Heisenberg group, arXiv:1411.4201 [math.GR], 2014; see Section 11.4.2. [There may be a typo in the recurrence given there]
FORMULA
G.f.: (1 + x + 4*x^2 + 11*x^3 + 8*x^4 + 21*x^5 + 6*x^6 + 9*x^7 + x^8)/((1-x)^4*(1+x+x^2)*(1+x^2)).
a(n) = (c_n + 31*n^3 - 57*n^2 + 105*n)/18 where c_n = -7, -14, 9, -16, -23, 18, -7, -32, 9, 2, -23, 0 for n >= 1, c_{n+12} = c_n. - R. J. Mathar, Sep 27 2016
MATHEMATICA
LinearRecurrence[{3, -4, 5, -6, 5, -4, 3, -1}, {1, 4, 12, 36, 82, 164, 294, 476, 724}, 40] (* Harvey P. Dale, Sep 02 2018 *)
CROSSREFS
Sequence in context: A374906 A357061 A190072 * A183931 A320967 A261584
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Aug 20 2001
STATUS
approved