David or Bob, What about this version of the sequence? a(1) = 1, a(n) = smallest number NOT YET IN THE SEQUENCE such that the concatenation of a(n-1) and a(n) is a square. It starts rather like A082209, 1, 6, 4, 9, 61, 504, 100, ... but it isn't in the OEIS. Oh, maybe it dies - could you check? Neil >