Kekulé numbers for certain benzenoids.

Terms

a(0) =1a(1) =18a(2) =140a(3) =700a(4) =2646a(5) =8232a(6) =22176a(7) =53460a(8) =117975a(9) =242242a(10) =468468a(11) =861224a(12) =1516060a(13) =2570400a(14) =4217088a(15) =6720984a(16) =10439037a(17) =15844290a(18) =23554300a(19) =34364484a(20) =49286930a(21) =69595240a(22) =96876000a(23) =133087500a(24) =180626355a(25) =242402706a(26) =321924708a(27) =423393040