OFFSET
1,3
COMMENTS
The sequence is constructed so that after the initial two 0's the next three pairs form a self-contained block beginning with 3, the subsequent nine pairs form a self-contained block beginning with 9, the following twenty-seven pairs form a block beginning with 27, etc. (powers of 3: A000244).
There are numerous sequences that satisfy the given criteria, so to fully define the continuation of this sequence I will add the following extra constraints. After the 0th block 0,0 the n-th block is found as follows: The block can be split into two halves such that one occurrence of each number appears in each half. The first half of the n-th block begins with 3^n then increases by consecutive integers until the maximum for that block: (3^(n+1) - 3)/2, before abruptly dropping to (3^n - 1)/2 and increasing by consecutive integers until (3^n - 1) is reached. The second half of the n-th block is then defined by the original constraints.
EXAMPLE
From the first and second appearances of 5 the sequence is 5, 6, 7, 8, 4, 9, 5 and as such has five numbers between the two 5's.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Elliott Line, Nov 10 2020
STATUS
approved