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A275386
The concatenation of |a(n)-a(n+1)| and a(n+1) is prime. Terms are distinct.
2
1, 3, 7, 9, 11, 17, 21, 23, 13, 19, 27, 29, 33, 47, 39, 41, 31, 57, 61, 37, 43, 63, 67, 53, 49, 51, 59, 69, 71, 77, 83, 79, 73, 81, 91, 87, 97, 109, 89, 101, 111, 113, 99, 1037, 121, 107, 93, 103, 123, 127, 129, 131, 119, 1023, 1031, 117, 1039, 133, 1009, 153, 157, 141, 143, 139, 137, 149, 159, 161, 151, 163, 171
OFFSET
1,2
COMMENTS
The sequence starts with a(1) = 1 and is always extended with the smallest integer not yet present that does not lead to a contradiction. This sequence is conjectured to be a permutation of the odd integers not ending with the digit “5”.
A variant of A275602
LINKS
EXAMPLE
|1-3| = 2 and 23 is prime; |3-7| = 4 and 47 is prime; |7-9| = 2 and 29 is prime; |9-11| = 2 and 211 is prime; |11-17| = 6 and 617 is prime; etc.
MATHEMATICA
a = {1}; Do[k = 1; While[Or[! PrimeQ@ FromDigits[IntegerDigits[Abs[a[[i - 1]] - k]]~Join~IntegerDigits[k]], MemberQ[a, k]], k++]; AppendTo[a, k], {i, 2, 71}]; a (* Michael De Vlieger, Nov 14 2016 *)
CROSSREFS
Sequence in context: A248667 A075607 A256465 * A275602 A173699 A287202
KEYWORD
nonn,base
AUTHOR
STATUS
approved