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

Terms

a(0) =0a(1) =0a(2) =2a(3) =15a(4) =84a(5) =431a(6) =2167a(7) =10847a(8) =54249a(9) =271262a(10) =1356331a(11) =6781678a(12) =33908414a(13) =169542094a(14) =847710496a(15) =4238552509a(16) =21192762578a(17) =105963812925a(18) =529819064661