Number of perfect matchings in graph C_3 x C_{2n}.

Terms

a(0) =50a(1) =224a(2) =1058a(3) =5054a(4) =24200a(5) =115934a(6) =555458a(7) =2661344a(8) =12751250a(9) =61094894a(10) =292723208a(11) =1402521134a(12) =6719882450a(13) =32196891104a(14) =154264573058a(15) =739125974174