A195516 - OEIS

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A195516

Number of lower triangles of an n X n -2..2 array with all row and column sums zero

0

1, 1, 5, 65, 3753, 860017, 839301197, 3535646416019, 65638445025610187, 5443595184898837903553

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Column 2 of A195522

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

Some solutions for n=4

..0........0........0........0........0........0........0........0

.-1.1.....-2.2.....-2.2......1-1......1-1......0.0......2-2......1-1

..0-2.2....1.0-1....2.0-2...-1-1.2....1-1.0...-1.2-1....0.2-2....0.0.0

..1.1-2.0..1-2.1.0..0-2.2.0..0.2-2.0.-2.2.0.0..1-2.1.0.-2.0.2.0.-1.1.0.0

CROSSREFS

Sequence in context: A195244 A162080 A012476 * A167536 A237887 A042491

Adjacent sequences: A195513 A195514 A195515 * A195517 A195518 A195519

KEYWORD

nonn

AUTHOR

R. H. Hardin Sep 20 2011

STATUS

approved