%I #8 Feb 26 2018 22:29:15
%S 2,2,6,22,58,146,414,1206,3410,9634,27670,79926,230666,667058,1936174,
%T 5632662,16408866,47875650,139908774,409404630,1199368026,3517351890,
%U 10325547582,30339113718,89217594738,262561101282,773248631222,2278737199606
%N Co-growth function of a certain group.
%D 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).
%F G.f. (x+1) * sqrt(1-x) / sqrt((1-3*x) * (3*x^2+1)) [from Humphries]. - _Sean A. Irvine_, Feb 26 2018
%K nonn
%O 1,1
%A _Stephen P. Humphries_
%E More terms from _Sean A. Irvine_, Feb 26 2018