A106473 Rows of A003989 expressed as base 10 numbers.

1, 11, 121, 1111, 12321, 111111, 1214121, 11311311, 121252121, 1111111111, 12341614321, 111111111111, 1212127212121, 11315311351311, 121412181214121, 1111111111111111, 12321612921612321, 111111111111111111

Offset: 0

Author

Paul Barry, May 03 2005

Keywords

• easy
• nonn
• base

Comments

The all-1 entries occur at positions indexed by the n-th primes-2 (A040976). The 1's then sum to give n-th prime-1 (A006093). The sum of the digits of a(n) is given by A006579(n+1).

Formula

a(n) = sum{k=0..n, GCD(n-k+1, k+1)*10^k}.