a(n) = (4*10^n - 31)/9.

A173768

a(n) = (4*10^n - 31)/9.

Terms

    a(0) =1a(1) =41a(2) =441a(3) =4441a(4) =44441a(5) =444441a(6) =4444441a(7) =44444441a(8) =444444441a(9) =4444444441a(10) =44444444441a(11) =444444444441

External references