Bisection of tribonacci numbers.

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =24a(5) =81a(6) =274a(7) =927a(8) =3136a(9) =10609a(10) =35890a(11) =121415a(12) =410744a(13) =1389537a(14) =4700770a(15) =15902591a(16) =53798080a(17) =181997601a(18) =615693474a(19) =2082876103a(20) =7046319384a(21) =23837527729a(22) =80641778674a(23) =272809183135a(24) =922906855808