Second trisection of A024494.

Terms

a(0) =2a(1) =10a(2) =86a(3) =682a(4) =5462a(5) =43690a(6) =349526a(7) =2796202a(8) =22369622a(9) =178956970a(10) =1431655766a(11) =11453246122a(12) =91625968982a(13) =733007751850