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A224333
T(n,k)=Number of idempotent n X n 0..k matrices of rank n-1
12
1, 1, 6, 1, 10, 21, 1, 14, 51, 60, 1, 18, 93, 212, 155, 1, 22, 147, 508, 805, 378, 1, 26, 213, 996, 2555, 2910, 889, 1, 30, 291, 1724, 6245, 12282, 10199, 2040, 1, 34, 381, 2740, 12955, 37494, 57337, 34984, 4599, 1, 38, 483, 4092, 24005, 93306, 218743, 262136
OFFSET
1,3
COMMENTS
Table starts
.....1......1.......1........1.........1.........1..........1..........1
.....6.....10......14.......18........22........26.........30.........34
....21.....51......93......147.......213.......291........381........483
....60....212.....508......996......1724......2740.......4092.......5828
...155....805....2555.....6245.....12955.....24005......40955......65605
...378...2910...12282....37494.....93306....201678.....393210.....708582
...889..10199...57337...218743....653177...1647079....3670009....7440167
..2040..34984..262136..1249992...4478968..13176680...33554424...76527496
..4599.118089.1179639..7031241..30233079.103766409..301989879..774840969
.10230.393650.5242870.39062490.201553910.807072130.2684354550.7748409770
LINKS
FORMULA
T(n,k) = 2*n*(1+k)^(n-1)-n
For column k:
k=1: a(n) = 6*a(n-1) -13*a(n-2) +12*a(n-3) -4*a(n-4)
k=2: a(n) = 8*a(n-1) -22*a(n-2) +24*a(n-3) -9*a(n-4)
k=3: a(n) = 10*a(n-1) -33*a(n-2) +40*a(n-3) -16*a(n-4)
k=4: a(n) = 12*a(n-1) -46*a(n-2) +60*a(n-3) -25*a(n-4)
k=5: a(n) = 14*a(n-1) -61*a(n-2) +84*a(n-3) -36*a(n-4)
k=6: a(n) = 16*a(n-1) -78*a(n-2) +112*a(n-3) -49*a(n-4)
k=7: a(n) = 18*a(n-1) -97*a(n-2) +144*a(n-3) -64*a(n-4)
For row n:
n=1: a(n) = 1
n=2: a(n) = 4*n + 2
n=3: a(n) = 6*n^2 + 12*n + 3
n=4: a(n) = 8*n^3 + 24*n^2 + 24*n + 4
n=5: a(n) = 10*n^4 + 40*n^3 + 60*n^2 + 40*n + 5
n=6: a(n) = 12*n^5 + 60*n^4 + 120*n^3 + 120*n^2 + 60*n + 6
n=7: a(n) = 14*n^6 + 84*n^5 + 210*n^4 + 280*n^3 + 210*n^2 + 84*n + 7
EXAMPLE
Some solutions for n=3 k=4
..1..1..0....0..0..0....1..0..0....1..0..4....1..0..0....0..3..1....0..3..0
..0..0..0....3..1..0....0..0..2....0..1..1....0..1..0....0..1..0....0..1..0
..0..2..1....1..0..1....0..0..1....0..0..0....1..2..0....0..0..1....0..0..1
CROSSREFS
Column 1 is A066524
Row 2 is A016825
Sequence in context: A336475 A082744 A127142 * A259671 A224524 A348982
KEYWORD
nonn,tabl
AUTHOR
R. H. Hardin, formula via M. F. Hasler William J. Keith and Rob Pratt in the Sequence Fans Mailing List, Apr 03 2013
STATUS
approved