a(n)=Product{k=0..n, 1+9^A010060(k)}/2.

Terms

a(0) =1a(1) =10a(2) =100a(3) =200a(4) =2000a(5) =4000a(6) =8000a(7) =80000a(8) =800000a(9) =1600000a(10) =3200000a(11) =32000000a(12) =64000000a(13) =640000000a(14) =6400000000a(15) =12800000000a(16) =128000000000a(17) =256000000000a(18) =512000000000