a(n) = n*Pell(n-2).

Terms

a(0) =0a(1) =1a(2) =0a(3) =3a(4) =8a(5) =25a(6) =72a(7) =203a(8) =560a(9) =1521a(10) =4080a(11) =10835a(12) =28536a(13) =74633a(14) =194040a(15) =501915a(16) =1292512a(17) =3315425a(18) =8474976a(19) =21597091a(20) =54884200a(21) =139127289a(22) =351877416a(23) =888121195a(24) =2237336592a(25) =5626467025a(26) =14126832720a(27) =35416929267a(28) =88670846936