Apparently an erroneous version of A007827.

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =13a(5) =33a(6) =73a(7) =202a(8) =488a(9) =1441a(10) =3741a(11) =11496a(12) =31311a(13) =98607a(14) =278840a(15) =895137a(16) =2599071a(17) =8452620