(A192249)/5.

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =60a(5) =186a(6) =522a(7) =1380a(8) =3459a(9) =8321a(10) =19332a(11) =43629a(12) =96045a(13) =206953a(14) =437677a(15) =910549a(16) =1866952a(17) =3778561a(18) =7558953a(19) =14963504a(20) =29340482a(21) =57033862a(22) =109989752a(23) =210575822a(24) =400452782a(25) =756836537a(26) =1422191570a(27) =2658250044a(28) =4943946756a(29) =9152396892