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Each term is a palindrome when written in base 2.

This entry is the result of merging two sequences. The old definition (which did not have the initial zero) was: "a(1)=1. For n >= 2, each a(n) = the decimal equivalent of either a(k)Ua(k) or a(k)U0Ua(k) or a(k)U1Ua(k), where U denotes concatenation of the binary representations of the arguments, and where k is some positive integer < n. The numbers are arranged in numerical order."