%I #2 Mar 30 2012 18:59:26
%S 1,0,-9,-81,-729,0,531441,43046721,3486784401,0,-205891132094649,
%T -150094635296999121,-109418989131512359209,0,
%U 523347633027360537213511521,3433683820292512484657849089281
%N Hankel transform of A174107 and A061639(n+1).
%F a(n)=((1/2-sqrt(2)/4)*(cos(3*pi*n/4)+sin(3*pi*n/4))+(1/2+sqrt(2)/4)*(cos(3*pi*n/4)-sin(3*pi*n/4)))*9^floor((n+1)^2/8).
%K easy,sign
%O 0,3
%A _Paul Barry_, Mar 07 2010