Number of edge covers of fan graph F_{1,n}.

Terms

a(0) =1a(1) =4a(2) =16a(3) =59a(4) =214a(5) =768a(6) =2745a(7) =9792a(8) =34900a(9) =124339a(10) =442906a(11) =1577540a(12) =5618665a(13) =20011452a(14) =71272296a(15) =253840779a(16) =904068526a(17) =3219889720a(18) =11467810393a(19) =40843217384a(20) =145465283884a(21) =518082304131