Duplicate of A023537.

Terms

a(0) =1a(1) =5a(2) =13a(3) =28a(4) =54a(5) =98a(6) =171a(7) =291a(8) =487a(9) =806a(10) =1324a(11) =2164a(12) =3525a(13) =5729a(14) =9297a(15) =15072