a(n) is the least number k such that 1/prime(k) has repeating decimal expansion of period n.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =26a(5) =13a(6) =4a(7) =52a(8) =21a(9) =28693a(10) =1128a(11) =2431a(12) =1221a(13) =16a(14) =71954a(15) =11a(16) =7a(17) =153888a(18) =8a(20) =496a(21) =14a(22) =9a(24) =5760923a(25) =2403a(26) =149a(27) =134a(28) =10a(29) =452a(30) =47a(31) =406