123231

Appears in sequences

• Concatenate (1,n,n,1).at n=23A100846
• Numbers k such that k divides 1 + Sum_{j=1..k} prime(j)^15.at n=20A233413
• Parent nodes of nonzero terms of A262509: a(n) = A049820(A262509(n)).at n=35A262510