221221

Appears in sequences

• Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,2,1.at n=5A037567
• k th digit of a(n) = number of different digits within 2 places of k (not including k).at n=22A039987
• n expressed in Fibonacci binary-like number system using only 1's and 2's.at n=29A108960
• Numbers such that each decimal digit d (for all d in the range 1 <= d <= 9) occurs only in runs of length exactly d.at n=21A140057
• Numbers for which the sum of reciprocals of square of digits is an integer.at n=23A182452
• List of imprimitive words over the alphabet {1,2}.at n=18A213972
• Shortest (x+1,2x)-code of n.at n=20A233135
• Non-primitive words on {1,2,3}.at n=33A239018
• Integers k such that k = Sum k/(p_i + j), where p_i are the prime factors of k (with multiplicity). Case j = -5.at n=9A380927