123467891011domain: NAppears in sequencesLet S(n) denote the sequence formed by concatenating the decimal numbers 1,2,3,..., omitting n; a(n) is the smallest prime in S(n), or -1 if no term in S(n) is prime.at n=4A262299Concatenation of the numbers from 1 to n but omitting 5.at n=9A262575