A220472 T(n,k)=Number of idempotent n X n -k..k matrices of rank 2

0, 0, 1, 0, 1, 75, 0, 1, 399, 4470, 0, 1, 927, 90390, 224810, 0, 1, 1815, 424374

Offset

1,6

Comments

Table starts

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

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

.....75...399....927.1815

...4470.90390.424374

.224810

Links

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

Example

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

Crossrefs

Row 3 is A223452

Sequence in context: A257534 A063680 A277841 * A033395 A143754 A357040

Adjacent sequences: A220469 A220470 A220471 * A220473 A220474 A220475

Keyword

nonn,tabl

Author

R. H. Hardin Apr 10 2013

Status

approved