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A355255
Irregular table read by rows: a(n,k) gives the number of distinct necklaces that appear in the following procedure: starting with the n-bead, (0,1)-necklace given by k written in binary, repeatedly take the first differences (mod 2) of the beads. 0 <= k < 2^n.
1
1, 1, 2, 1, 3, 3, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 5, 5, 4, 5, 3, 4, 5, 5, 4, 3, 5, 4, 5, 5, 2, 1, 4, 4, 3, 4, 3, 3, 4, 4, 3, 3, 4, 3, 4, 4, 3, 4, 3, 3, 4, 3, 4, 4, 3, 3, 4, 4, 3, 4, 3, 3, 2, 1, 4, 4, 3, 4, 2, 3, 3, 4, 2, 2, 4, 3, 4, 3, 2, 4, 2, 2, 4, 2, 3, 4, 3, 3, 4, 4, 1, 3, 3, 2, 4, 4, 3, 2, 3, 2, 4, 4, 2, 2, 4, 3, 3, 4, 1, 3, 4, 3, 3, 4, 2, 4, 3, 1, 4, 3, 2, 3, 4, 2, 4, 4, 2
OFFSET
0,3
COMMENTS
For j >= 1, the sequence a(j,1) begins
2, 3, 2, 5, 4, 4, 8, 9, 8, 8, 32, 8, 64, 16, 16, 17, 16, 16, 512, 16, 64, 64, 2048, 16, 1024, 128, 512, 32, 16384, 32, ...
Conjecture: a(2^m,1) = 2^m + 1 for all m > 1.
Conjecture: a(m,1) is a power of 2 whenever m is not a power of 2.
The sequence of the number of distinct values in the n-th row begins 1, 2, 3, 2, 5, 4, 4, 4, 9, 4, 8, 4, 8, 4, 10, 6, 17, 6, 10, ... - Peter Kagey, Jul 03 2022
EXAMPLE
Table begins:
n\k | 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
----+-----------------------------------------------
0 | 1;
1 | 1, 2;
2 | 1, 3, 3, 2;
3 | 1, 2, 2, 1, 2, 1, 1, 2;
4 | 1, 5, 5, 4, 5, 3, 4, 5, 5, 4, 3, 5, 4, 5, 5, 2;
... | ...
a(5,13) = 4 because 13 is 01101 in binary; the sequence of first differences is 01101, 10111, 11000, 01001, 11011, ...; and 10111 is the same necklace as 11011.
CROSSREFS
Sequence in context: A355686 A308530 A302555 * A336692 A332434 A262209
KEYWORD
nonn,tabf,base,look
AUTHOR
Peter Kagey, Jun 26 2022
STATUS
approved