a(n) is the index of the first occurrence of n in A166006.

Terms

a(0) =1a(1) =2a(2) =21a(3) =6594a(4) =6595a(5) =6602a(6) =6603a(7) =6604a(8) =6605a(9) =6606a(10) =6609a(11) =6612a(12) =6613a(13) =6622a(14) =6623a(15) =6626a(16) =6627a(17) =6628a(18) =6629a(19) =6630a(20) =7499a(21) =7500a(22) =7507a(23) =7512a(24) =7513a(25) =7514a(26) =7535a(27) =7536a(28) =7537a(29) =27056