Number of perfect matchings in the P_4 X C_n graph.

Terms

a(0) =19a(1) =121a(2) =176a(3) =725a(4) =1471a(5) =5041a(6) =11989a(7) =37584a(8) =97021a(9) =290521a(10) =783511a(11) =2289869a(12) =6323504a(13) =18241441a(14) =51026011a(15) =146160725a(16) =411720121a(17) =1174844176a(18) =3322046089a(19) =9459791909a(20) =26804466571a(21) =76241702161a(22) =216275875376a(23) =614789884829