A343538 Longest sequence of distinct two-digit numbers (10-99) such that any two or three consecutive terms can be concatenated into a prime number, even when connected into a loop. Smallest number is listed first.

13, 61, 63, 67, 19, 99, 31, 69, 91, 87, 79, 37, 39, 43, 27, 49, 73, 51

Offset

1,1

Comments

A total of 164 sequences exist from two to eighteen terms. Checked to a depth of 50 terms with two different programs. 11262 sequences with two to twenty-one terms exist if the demand on connecting the sequence into a loop is removed.

References

Andreas Boe, The Toy Robot, Amazon, 2014, Afterword Quiz.

Links

Table of n, a(n) for n=1..18.

Andreas Boe, All 2-digit looped sequences

Illustration for 11,17,33,47,93,71,51,53,81,23,41,39

Example

13,61,63,67 -> 1361, 6163, 6367, 136163, 616367 are all prime numbers.

Crossrefs

Sequence in context: A228282 A303806 A304853 * A305250 A304542 A228558

Adjacent sequences: A343535 A343536 A343537 * A343539 A343540 A343541

Keyword

nonn,base,fini,full

Author

Andreas Boe, Apr 18 2021

Status

approved