Nonprime concatenations of divisors of some k, ordered by k.

Terms

a(0) =1a(1) =12a(2) =124a(3) =15a(4) =1236a(5) =1248a(6) =12510a(7) =111a(8) =1234612a(9) =12714a(10) =13515a(11) =124816a(12) =117a(13) =1236918a(14) =119a(15) =12451020a(16) =121122a(17) =123a(18) =1234681224a(19) =1525a(20) =121326a(21) =13927a(22) =12471428a(23) =129a(24) =12356101530a(25) =12481632a(26) =131133a(27) =121734a(28) =15735a(29) =123469121836