A075610 a(1) = 1, a(n) = smallest prime number not occurring earlier such that the concatenation a(n-1) and a(n) is a composite number.
1, 2, 5, 7, 11, 13, 3, 19, 17, 29, 23, 31, 41, 37, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 97, 89, 103, 101, 109, 107, 113, 127, 131, 137, 139, 149, 151, 167, 157, 173, 163, 179, 181, 191, 193, 197, 199, 223, 227, 211, 233, 229, 239, 241, 251, 269, 263, 271, 257, 277
Offset: 1
Extensions
More terms from Michel ten Voorde Jun 23 2003