Wonderful Demlo numbers: a(n) = ((10^n - 1)/9)^2.

A002477

Wonderful Demlo numbers: a(n) = ((10^n - 1)/9)^2.

Terms

    a(0) =1a(1) =121a(2) =12321a(3) =1234321a(4) =123454321a(5) =12345654321

External references