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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
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
1,2
LINKS
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.
CROSSREFS
Cf. A152607.
Sequence in context: A003033 A193945 A087147 * A337613 A152607 A118559
KEYWORD
base,nonn
AUTHOR
Eric Angelini, Aug 17 2023
STATUS
approved