A363572 Lexicographically earliest sequence of distinct terms > 0 such that the concatenation of the rightmost digit of a(n) and the leftmost digit of a(n+1) forms a prime number. The rightmost digit of a(n) cannot be 0.

1, 3, 7, 9, 71, 11, 12, 31, 13, 14, 15, 32, 33, 16, 17, 18, 34, 19, 72, 35, 36, 73, 74, 37, 38, 39, 75, 91, 76, 77, 92, 93, 78, 94, 79, 701, 95, 96, 101, 97, 98, 99, 702, 301, 102, 302, 303, 103, 104, 105, 304, 106, 107, 108, 305, 306, 109, 703, 111, 112, 307, 113, 114, 115

Offset: 1

Author

Eric Angelini, Aug 17 2023

Keywords

• base
• nonn

Examples

			a(1) = 1 and a(2) = 3 form 13, a prime number;
a(2) = 3 and a(3) = 7 form 37, a prime number;
a(3) = 7 and a(4) = 9 form 79, a prime number;
a(4) = 9 and the leftmost digit of a(5) = 71 form 97, a prime number;
a(5) = 71 and its rightmost digit, concatenated to the leftmost digit of a(6) = 11, form 11, a prime number; etc.
		

Links

• Tyler Busby, Table of n, a(n) for n = 1..10000
• Eric Angelini, Prime welds, Personal blog.

Crossrefs

Cf. A152607.