121211

Appears in sequences

• Periodic points under the map A053392 that adds consecutive pairs of digits and concatenates them.at n=32A053393
• Concatenate (1,n,n,1).at n=21A100846
• n expressed in Fibonacci binary-like number system using only 1's and 2's.at n=23A108960
• Composite numbers whose product of digits is 4.at n=39A201016
• List of subwords of A003842 arranged in lexicographic order.at n=23A213975
• Elements of the Motzkin words sub-operad Motz of TN generated by 00 and 010.at n=28A231872
• Positive numbers n such that (digitsum(n))^2 equals (product of digits(n))^3.at n=14A261778
• 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=35A273978
• 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=15A307312
• 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=37A336528