122220

Appears in sequences

• Expansion of (1-x^7)/(1-x)^7.at n=18A008489
• Numbers n such that phi(n) is the sum of the first k divisors of n for some k.at n=25A072278
• Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in cycle of length=11.at n=18A096888
• a(n) is the number of 2-regular 3-hypergraphs on 3n labeled vertices. (In a 3-hypergraph, each hyper-edge is a proper 3-set; 2-regular implies that each vertex is in exactly 2 hyperedges.)at n=3A110100
• a(n) is the smallest positive multiple of n whose decimal digits are all 0, 1 or 2.at n=44A181060
• Ternary numbers consisting of a run of 1's, then a run of 2's, then a run of 0's.at n=19A371051
• Ternary numbers that are concatenated runs A(1)C(1)B(1)A(2)C(2)B(2)...A(k)C(k)B(k), where A(i) is a run of 1's, B(i) a run of 0's, and C(i) a run of 2's, for i = 1..k.at n=20A371107