Partial sums of round(5^n/7).

Terms

a(0) =0a(1) =1a(2) =5a(3) =23a(4) =112a(5) =558a(6) =2790a(7) =13951a(8) =69755a(9) =348773a(10) =1743862a(11) =8719308a(12) =43596540a(13) =217982701a(14) =1089913505a(15) =5449567523a(16) =27247837612a(17) =136239188058a(18) =681195940290