Bond percolation series for hexagonal net.

Terms

a(0) =1a(1) =-1a(2) =-4a(3) =-12a(4) =-45a(5) =-188a(6) =-835a(7) =-3849a(8) =-18242a(9) =-88265a(10) =-434295a(11) =-2165198a(12) =-10915089a(13) =-55534781a(14) =-284708699a(15) =-1470350760a(16) =-7628363273a(17) =-39878267745a(18) =-208458228964