A007985 Co-growth function of a certain group.

2, 2, 6, 22, 58, 146, 414, 1206, 3410, 9634, 27670, 79926, 230666, 667058, 1936174, 5632662, 16408866, 47875650, 139908774, 409404630, 1199368026, 3517351890, 10325547582, 30339113718, 89217594738, 262561101282, 773248631222, 2278737199606

Offset

1,1

References

Stephen P Humphries, "Cogrowth of groups and the Dedekind-Frobenius group determinant", Mathematical Proceeding of the Cambridge Philosophical Society volume 121 Part 2 pages 193-217 (1997).

Links

Table of n, a(n) for n=1..28.

Formula

G.f. (x+1) * sqrt(1-x) / sqrt((1-3*x) * (3*x^2+1)) [from Humphries]. - Sean A. Irvine, Feb 26 2018

Crossrefs

Sequence in context: A004077 A271217 A202743 * A097090 A085403 A112478

Adjacent sequences: A007982 A007983 A007984 * A007986 A007987 A007988

Keyword

nonn

Author

Stephen P. Humphries

Extensions

More terms from Sean A. Irvine, Feb 26 2018

Status

approved