121122

Appears in sequences

• Replace n with concatenation of its divisors.at n=21A037278
• Sorted list of strings that can be obtained by starting with 12 and repeatedly doubling any substring in place.at n=24A130838
• Nonprime concatenations of divisors of some k, ordered by k.at n=16A176556
• Triangle read by rows in which row n lists the binary words of length n over the alphabet {1,2} with no initial repeats.at n=28A211029
• List of subwords (or factors) of the Thue-Morse "1,2"-word A001285.at n=38A214215
• List of words over {1,2} with equal numbers of 1's and 2's.at n=12A214218
• List of words of length n over an alphabet of size 9 that are in standard order and which have the property that every letter that appears in the word is repeated.at n=34A273978
• Consider the Post tag system described in A284116 (but adapted to the alphabet {1,2}) ; sequence lists the words that terminate in the empty word.at n=43A289675
• Expansion of 1/(1 - Sum_{p prime, k>=1} x^(p^k)/(1 - x^(p^k))).at n=24A300672
• a(1) = 1; a(2) = 2; for n > 2, a(n) is the least number > a(n-1) whose decimal representation is uniquely the concatenation of the decimal representations of two distinct earlier terms.at n=36A336528
• The word 1 belongs to the sequence, and whenever a word w belongs to the sequence, then the words consisting of 1's and 2's whose run lengths transform equals w also belong to the sequence.at n=25A376637
• List of subwords (or factors) of the Kolakoski sequence (A000002).at n=40A376677