A363572 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Tyler Busby, Table of n, a(n) for n = 1..10000

Eric Angelini, Prime welds, Personal blog.

EXAMPLE

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.