212122

Appears in sequences

• Numbers for which the sum of reciprocals of square of digits is an integer.at n=18A182452
• Shortest (x+1,2x)-code of n.at n=27A233135
• Reversed shortest (x+1,2x)-code of n.at n=21A233137
• Take n-th string over {1,2} in lexicographic order and apply the Watanabe tag system {00, 1011} described in A291067 (but adapted to the alphabet {1,2}) just once.at n=48A291072
• Triangle read by rows: T(n,k) is the number of face-connected polyhedral components consisting of k cuboctahedra and n-k octahedra in the rectified cubic honeycomb up to translation, rotation, and reflection of the honeycomb, 0<=k<=n.at n=53A384782