a(n) = 6*7^n+1.

Terms

a(0) =7a(1) =43a(2) =295a(3) =2059a(4) =14407a(5) =100843a(6) =705895a(7) =4941259a(8) =34588807a(9) =242121643a(10) =1694851495a(11) =11863960459a(12) =83047723207a(13) =581334062443