Smallest integer not the sum of nonzero powers of previous terms.

Terms

a(0) =1a(1) =2a(2) =6a(3) =12a(4) =24a(5) =54a(6) =108a(7) =246a(8) =510a(9) =1218a(10) =2742a(11) =6930a(12) =16242a(13) =47706a(14) =144018a(15) =672732a(16) =2756124a(17) =5656266a(18) =27943404a(19) =75554226a(20) =661653378a(21) =1323306756