Duplicate of A077843.

Terms

a(0) =1a(1) =1a(2) =4a(3) =12a(4) =34a(5) =100a(6) =292a(7) =852a(8) =2488a(9) =7264a(10) =21208a(11) =61920a(12) =180784a(13) =527824a(14) =1541056a(15) =4499328