a(n) = A000522(n) - 2.

Terms

a(0) =0a(1) =3a(2) =14a(3) =63a(4) =324a(5) =1955a(6) =13698a(7) =109599a(8) =986408a(9) =9864099a(10) =108505110a(11) =1302061343a(12) =16926797484a(13) =236975164803