Nonprimes formed by concatenation of the decimal digits of a nonprime and its index.

Terms

a(0) =1a(1) =12a(2) =64a(3) =85a(4) =96a(5) =128a(6) =1510a(7) =1611a(8) =1812a(9) =2013a(10) =2114a(11) =2215a(12) =2416a(13) =2517a(14) =2618a(15) =2820a(16) =3021a(17) =3222a(18) =3424a(19) =3525a(20) =3626a(21) =3827a(22) =3928a(23) =4029a(24) =4230a(25) =4431a(26) =4532a(27) =4633a(28) =4834a(29) =4935