A220473 T(n,k)=Number of idempotent n X n -k..k matrices of rank n-2

0, 0, 1, 0, 1, 87, 0, 1, 447, 4470, 0, 1, 999, 90390, 172850, 0, 1, 1935, 424374

Offset

1,6

Comments

Table starts

......0.....0......0....0.0.0

......1.....1......1....1.1

.....87...447....999.1935

...4470.90390.424374

.172850

Links

Table of n, a(n) for n=1..19.

Example

Some solutions for n=3 k=4
.-2..0.-3....2.-2.-2...-1.-1.-3....0..0..0....0..0..0...-1.-2..2....3..4.-2
.-2..0.-3....4.-4.-4...-1.-1.-3....0.-3.-4....0..2..1....1..2.-2...-3.-4..2
..2..0..3...-3..3..3....1..1..3....0..3..4....0.-2.-1....0..0..0...-3.-4..2

Crossrefs

Row 3 is A221312

Sequence in context: A093243 A223814 A262419 * A067157 A077511 A036190

Adjacent sequences: A220470 A220471 A220472 * A220474 A220475 A220476

Keyword

nonn,tabl

Author

R. H. Hardin Apr 10 2013

Status

approved