A298807 Growth series for group with presentation < S, T : S^3 = T^3 = (S*T)^6 = 1 >.

1, 4, 8, 16, 32, 64, 126, 242, 472, 920, 1792, 3486, 6788, 13216, 25730, 50092, 97518, 189860, 369628, 719612, 1400980, 2727504, 5310068, 10337932, 20126468, 39183340, 76284330, 148514636, 289136638, 562907480, 1095899956, 2133559698, 4153734080, 8086723216, 15743687792, 30650697262, 59672502090

Offset: 0

Author

John Cannon and N. J. A. Sloane, Feb 04 2018

Keywords

• nonn
• easy

Links

• Colin Barker, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (0,1,2,3,5,3,2,1,0,-1).

Crossrefs

Cf. A008579, A298802, A298805.

Programs

Magma

// See Magma program in A298805.

Mathematica

LinearRecurrence[{0,1,2,3,5,3,2,1,0,-1},{1,4,8,16,32,64,126,242,472,920,1792,3486},40] (* Harvey P. Dale, Jul 02 2025 *)

PARI

Vec((1 + 4*x + 7*x^2 + 10*x^3 + 13*x^4 + 15*x^5 + 15*x^6 + 12*x^7 + 9*x^8 + 6*x^9 + 3*x^10 - 2*x^11) / ((1 + x + x^2 + x^3 + x^4)*(1 - x - x^2 - x^3 - x^4 - x^5 + x^6)) + O(x^40)) \\ Colin Barker, Feb 06 2018

Formula

G.f.: (-2*x^11 + 3*x^10 + 6*x^9 + 9*x^8 + 12*x^7 + 15*x^6 + 15*x^5 + 13*x^4 + 10*x^3 + 7*x^2 + 4*x + 1)/(x^10 - x^8 - 2*x^7 - 3*x^6 - 5*x^5 - 3*x^4 - 2*x^3 - x^2 + 1).

a(n) = a(n-2) + 2*a(n-3) + 3*a(n-4) + 5*a(n-5) + 3*a(n-6) + 2*a(n-7) + a(n-8) - a(n-10) for n>11. - Colin Barker, Feb 06 2018