a(n) = 3^^(n+1) modulo 10^n.

Terms

a(0) =7a(1) =87a(2) =387a(3) =5387a(4) =95387a(5) =195387a(6) =4195387a(7) =64195387a(8) =464195387a(9) =2464195387a(10) =62464195387a(11) =262464195387