2121211

Appears in sequences

• Underline all even terms; concatenations of underlined terms and of non-underlined terms both equal the concatenation of the entire sequence. This is the lexicographically earliest such sequence without duplicate terms and with an even digit among the first two terms.at n=30A307312
• List of co-Lyndon words on {1,2} sorted first by length and then lexicographically.at n=26A329318