Partial sums of round(5^n/9).

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =87a(5) =434a(6) =2170a(7) =10851a(8) =54254a(9) =271268a(10) =1356337a(11) =6781684a(12) =33908420a(13) =169542101a(14) =847710504a(15) =4238552518a(16) =21192762587a(17) =105963812934a(18) =529819064670