122121

Appears in sequences

• Expansion of g.f. 1/((1-x)*(1-5*x)*(1-10*x)*(1-12*x)).at n=4A023947
• Fibonacci sequence in base 2 of the alternate number system.at n=10A085652
• n expressed in Fibonacci binary-like number system using only 1's and 2's.at n=27A108960
• 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=31A211029
• List of subwords (or factors) of the Thue-Morse "1,2"-word A001285.at n=41A214215
• List of words over {1,2} with equal numbers of 1's and 2's.at n=16A214218
• Elements of the Motzkin words sub-operad Motz of TN generated by 00 and 010.at n=31A231872
• 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=46A289675
• Unique representation of nonnegative numbers by iterated tribonacci A, B and C sequences.at n=53A316713
• a(0) = 12; thereafter a(n) is the concatenation of A328991(n),2,A328991(n-1).at n=1A328992