OFFSET
0,2
COMMENTS
This is the Poincaré series [or Poincare series] for the quasi-Lannér diagram QL4_1 - see Tables 7.6, 7.7 and 7.8 in Maxim Chapovalov, Dimitry Leites and Rafael Stekolshchik (2009), or equivalently Tables 5 and 6 in the shorter version, Maxim Chapovalov, Dimitry Leites and Rafael Stekolshchik (2010).
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Maxim Chapovalov, Dimitry Leites, and Rafael Stekolshchik, The Poincaré series [or Poincare series] of the hyperbolic Coxeter groups with finite volume of fundamental domains, arXiv:0906.1596 [math.RT], 2009.
Maxim Chapovalov, Dimitry Leites, and Rafael Stekolshchik, The Poincaré series [or Poincare series] of the hyperbolic Coxeter groups with finite volume of fundamental domains, Journal of Nonlinear Mathematical Physics 17.supp01 (2010): 169-215.
Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,0,0,0,-1).
FORMULA
G.f.: (1 + x^2)*(1 - x + x^2)*(1 + x + x^2)*(1 + x)^3/((1 - x)*(1 - x^4 - x^5 - x^6 - x^7)). [Bruno Berselli, Dec 28 2015]
MATHEMATICA
Join[{1, 4}, LinearRecurrence[{1, 0, 0, 1, 0, 0, 0, -1}, {9, 16, 25, 37, 53, 74, 101, 135}, 50]] (* Jean-François Alcover, Jan 08 2019 *)
PROG
(Magma) /* By definition: */ m:=50; R<x>:=PowerSeriesRing(Integers(), m); b:=func<k|(1-x^k)/(1-x)>; Coefficients(R!(b(2)*b(4)*b(6)/(x^8-x^4-x+1))); // Bruno Berselli, Dec 28 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Dec 27 2015
STATUS
approved