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A063812 Growth series for fundamental group of orientable closed surface of genus 2. 1
1, 8, 56, 392, 2736, 19096, 133288, 930328, 6493536, 45323816, 316352792, 2208090536, 15412109328, 107573992120, 750848799112, 5240801312824, 36579932515008, 255321921769544, 1782105084785144, 12438800833105352 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

REFERENCES

P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 160, Sigma(Gamma_2, S_2; z).

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (6,6,6,-1).

FORMULA

G.f.: (1 + x)^2*(1 + x^2) / (1 - 6*x - 6*x^2 - 6*x^3 + x^4).

a(n) = 6*a(n-1) + 6*a(n-2) + 6*a(n-3) - a(n-4) for n>4. - Colin Barker, Jun 13 2019

PROG

(PARI) Vec((1 + x)^2*(1 + x^2) / (1 - 6*x - 6*x^2 - 6*x^3 + x^4) + O(x^20)) \\ Colin Barker, Jun 13 2019

CROSSREFS

Sequence in context: A010556 A010575 A162949 * A234274 A163347 A163924

Adjacent sequences:  A063809 A063810 A063811 * A063813 A063814 A063815

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Aug 21 2001

STATUS

approved

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Last modified February 18 15:30 EST 2020. Contains 332019 sequences. (Running on oeis4.)