A252970 Number of nX2 nonnegative integer arrays with upper left 0 and lower right n+2-5 and value increasing by 0 or 1 with every step right or down.
0, 0, 1, 13, 61, 192, 483, 1050, 2058, 3732, 6369, 10351, 16159, 24388, 35763, 51156, 71604, 98328, 132753, 176529, 231553, 299992, 384307, 487278, 612030, 762060, 941265, 1153971, 1404963, 1699516, 2043427, 2443048, 2905320, 3437808, 4048737
Offset: 1
Keywords
Examples
Some solutions for n=4 ..0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..0....0..1....0..1 ..0..1....0..0....0..0....1..1....0..0....0..1....0..1....0..0....1..1....0..1 ..0..1....0..0....0..0....1..1....1..1....0..1....0..1....0..1....1..1....0..1 ..1..1....0..1....1..1....1..1....1..1....0..1....0..1....0..1....1..1....1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = (1/720)*n^6 + (7/240)*n^5 - (1/144)*n^4 - (31/48)*n^3 + (271/180)*n^2 - (53/60)*n = n*(n-1)*(n-2)*(n^3+24*n^2+65*n-318)/720.
Empirical: G.f.: -x^3*(1+6*x-9*x^2+3*x^3) / (x-1)^7 . - R. J. Mathar, Nov 23 2015
Comments