|
|
A202865
|
|
Number of 3 X 3 0..n arrays with row and column sums one greater than the previous row and column.
|
|
1
|
|
|
2, 42, 228, 776, 2046, 4578, 9128, 16704, 28602, 46442, 72204, 108264, 157430, 222978, 308688, 418880, 558450, 732906, 948404, 1211784, 1530606, 1913186, 2368632, 2906880, 3538730, 4275882, 5130972, 6117608, 7250406, 8545026
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
Empirical: a(n) = (3/10)*n^5 + (3/2)*n^4 + (3/2)*n^3 - (1/2)*n^2 - (4/5)*n.
G.f.: 2*x*(1 + 15*x + 3*x^2 - x^3) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
|
|
EXAMPLE
|
Some solutions for n=7:
6 5 2 2 5 4 1 7 4 4 4 2 2 2 1 6 3 0 2 6 2
6 2 6 3 5 4 5 1 7 1 4 6 0 0 6 2 2 6 3 4 4
1 7 7 6 2 5 6 5 3 5 3 4 3 4 0 1 5 5 5 1 6
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|