Total number of round trips, each of length 2*n on the graph P_5 (o-o-o-o-o).

Terms

a(0) =5a(1) =8a(2) =20a(3) =56a(4) =164a(5) =488a(6) =1460a(7) =4376a(8) =13124a(9) =39368a(10) =118100a(11) =354296a(12) =1062884a(13) =3188648a(14) =9565940a(15) =28697816a(16) =86093444a(17) =258280328a(18) =774840980a(19) =2324522936a(20) =6973568804a(21) =20920706408a(22) =62762119220a(23) =188286357656a(24) =564859072964