a(n) = (1/2)*(F(n+2)-1)*(F(n+2)-2) + F(n), where F() are the Fibonacci numbers.

Terms

a(0) =1a(1) =2a(2) =8a(3) =24a(4) =71a(5) =198a(6) =541a(7) =1452a(8) =3862a(9) =10208a(10) =26885a(11) =70644a(12) =185369a(13) =485982a(14) =1273420a(15) =3335640a(16) =8735707a(17) =22875050a(18) =59895221a(19) =156819960a(20) =410579786a(21) =1074943872a(22) =2814291433a(23) =7367994504a(24) =19289795761a(25) =50501560538a(26) =132215157296a(27) =346144350552a(28) =906218605007