212121212

Appears in sequences

• Two-bell analog of A028355.at n=13A028359
• Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,1.at n=8A037495
• a(n) is the largest base-3 string such that the n-th number coprime to 3 does not divide any substring of a(n).at n=6A114880
• a(n) is the smallest number not already present that permits the cyclic repetition of the path 1,2 of the digits in the sequence.at n=17A165300