1213121

Appears in sequences

• Concatenation of terms of A018238.at n=2A082215
• Palindromes p such that 5p + 1 is also a palindrome.at n=16A083833
• Palindromes n such that 6n + 1 is also a palindrome.at n=16A083835
• Apply the tribonacci morphism 1 -> {1, 2}, 2 -> {1, 3}, 3 -> {1} n times to 1, and concatenate the resulting string.at n=3A103269
• a(n) is the smallest number consisting of digits {1,...,n} that contains all the permutations of {1,...,n} as subsequences.at n=2A136094
• a(n) is the concatenation of A103269(n-i) for i = 0,1,2,...,n-1.at n=2A317197
• Working over the alphabet {1,2,3}, start with a(1) = 1; then a(n+1) is made by inserting a letter into a(n) at the rightmost possible position which makes a squarefree word (and the smallest letter if multiple letters are possible at that place).at n=6A332603