112221

Appears in sequences

• a(n) = 100*n^2 + 100*n + 21.at n=33A152161
• 6-digit numbers k such that: (a) the digits of k are from the set {1, 2, 3, 4, 5}, and (b) any digit that appears in k appears at least twice.at n=22A171725
• List of words over {1,2} with equal numbers of 1's and 2's.at n=11A214218
• Elements of the Motzkin words sub-operad Motz of TN generated by 00 and 010.at n=24A231872
• 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=27A273978
• Unique representation of nonnegative numbers by iterated tribonacci A, B and C sequences.at n=61A316713
• Number of symmetric binary n X n matrices with no 2 X 2 submatrix of all 1s.at n=5A352258