OFFSET
2,1
COMMENTS
The irregular array of numbers is:
....k..3...4...5...6...7...8...9..10..11..12..13..14..15..16..17
..n
..2....4
..3....4...4...2
..4....4...4...6...6
..5....4...4...6..10..10...2
..6....4...4...6..10..14..16...8
..7....4...4...6..10..14..20..26..18...2
..8....4...4...6..10..14..20..30..40..34..10
..9....4...4...6..10..14..20..30..44..60..60..28...2
.10....4...4...6..10..14..20..30..44..64..90.100..62..12
.11....4...4...6..10..14..20..30..44..64..94.134.160.122..40...2
where k is the path length in nodes.
In an attempt to define the irregularity of the array, it appears that the maximum value of k is (3n + n mod 2)/2 for n >= 2.
Reading this array by rows gives the sequence.
One half of the numbers of paths constitute the sequence to remove the effect of the bilateral symmetry of a rectangle.
LINKS
FORMULA
The asymptotic sequence for the number of paths of each nodal length k for n >> 0 appears to be 2*A097333(1:), that is, 2*(Sum(j=0..k-2, C(k-2-j, floor(j/2)))), for k >= 3.
EXAMPLE
T(2,3) = One half of the number of complete non-self-adjacent simple paths of length 3 nodes within a square lattice bounded by a 2 X 2 node rectangle.
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Christopher Hunt Gribble, Jun 08 2012
STATUS
approved