393939

Appears in sequences

• Numbers whose consecutive digits differ by 6.at n=40A048408
• Smallest multiple of n^2 beginning and ending in n, or 0 if no such multiple exists.at n=38A078211
• After a(1) = 1, the sequence is always extended with the smallest divisor d (not yet present in the sequence) of the last term t. If d doesn't exist, we extend the sequence with tt (t concatenated to itself). If tt doesn't produce a new d, we extend the sequence with ttt, etc. See the Comments section for more details.at n=28A348871