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A282666 The larger term of the pair (a(n), a(n+1)) is always prime and the larger digit of any pair of adjacent digits is also prime. 1
0, 2, 1, 3, 5, 4, 7, 6, 71, 20, 23, 12, 13, 17, 15, 31, 21, 37, 22, 53, 25, 47, 27, 67, 30, 73, 32, 127, 33, 131, 35, 137, 45, 151, 50, 223, 51, 227, 52, 157, 54, 503, 55, 173, 57, 233, 70, 251, 72, 257, 74, 521, 75, 271, 76, 727, 77, 277, 120, 307, 121, 313, 122, 317, 123, 331, 202, 337, 125, 353, 130, 373, 132, 523, 133, 547, 135 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The sequence is started with a(1) = 0 and always extended with the smallest integer not yet present and not leading to a contradiction.

If two successive digits are equal (e.g., 2,2) we accept that there is a "larger one" (2).

The digits "8" and "9" cannot be present in the sequence as no "prime digit" is larger than "8" or "9".

LINKS

Jean-Marc Falcoz, Table of n, a(n) for n = 1..7853

EXAMPLE

In the 1st pair of integers (0,2) the larger term is 2, which is prime;

in the 2nd pair of integers (2,1) the larger term is 2, which is prime;

in the 3rd pair of integers (1,3) the larger term is 3, which is prime;

in the 4th pair of integers (3,5) the larger term is 5, which is prime;

...

in the 9th pair of integers (71,20) the larger term is 71, which is prime;

in the 10th pair of integers (20,23) the larger term is 23, which is prime;

in the 11th pair of integers (23,12) the larger term is 23, which is prime; etc.

In the 1st pair of digits (0,2) the larger digit is 2, which is prime;

in the 2nd pair of digits (2,1) the larger digit is 2, which is prime;

in the 3rd pair of digits (1,3) the larger digit is 3, which is prime;

in the 4th pair of digits (3,5) the larger digit is 5, which is prime;

...

in the 9th pair of digits (7,1) the larger digit is 7, which is prime;

in the 10th pair of digits (1,2) the larger digit is 2, which is prime;

in the 11th pair of digits (2,0) the larger digit is 2, which is prime; etc.

CROSSREFS

Sequence in context: A234751 A113790 A181094 * A181560 A250103 A063705

Adjacent sequences:  A282663 A282664 A282665 * A282667 A282668 A282669

KEYWORD

nonn,base

AUTHOR

Eric Angelini and Jean-Marc Falcoz, Feb 20 2017

STATUS

approved

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Last modified October 24 20:07 EDT 2020. Contains 338009 sequences. (Running on oeis4.)