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A156525
Number of n X n arrays of squares of integers, symmetric about main diagonal, with all rows summing to 81.
0
1, 2, 24, 552, 39012, 11870808, 25684597626, 1292153534554332
OFFSET
1,2
EXAMPLE
From Neven Juric, Mar 01 2010: To illustrate a(3) =24:
{(0,0,81),(0,81,0),(81,0,0)}
{(0,81,0),(81,0,0),(0,0,81)}
{(1,16,64),(16,49,16),(64,16,1)}
{(1,16,64),(16,64,1),(64,1,16)}
{(1,64,16),(64,1,16),(16,16,49)}
{(1,64,16),(64,16,1),(16,1,64)}
{(9,36,36),(36,9,36),(36,36,9)}
{(9,36,36),(36,36,9),(36,9,36)}
{(16,1,64),(1,64,16),(64,16,1)}
{(16,16,49),(16,49,16),(49,16,16)}
{(16,49,16),(49,16,16),(16,16,49)}
{(16,64,1),(64,1,16),(1,16,64)}
{(36,9,36),(9,36,36),(36,36,9)}
{(36,36,9),(36,9,36),(9,36,36)}
{(49,16,16),(16,1,64),(16,64,1)},
{(49,16,16),(16,16,49),(16,49,16)}
{(49,16,16),(16,49,16),(16,16,49)}
{(49,16,16),(16,64,1),(16,1,64)}
{(64,1,16),(1,16,64),(16,64,1)}
{(64,1,16),(1,64,16),(16,16,49)}
{(64,16,1),(16,1,64),(1,64,16)}
{(64,16,1),(16,49,16),(1,16,64)}
{(81,0,0),(0,0,81),(0,81,0)}
{(81,0,0),(0,81,0),(0,0,81)}
CROSSREFS
Sequence in context: A000186 A210905 A012113 * A377490 A377492 A377425
KEYWORD
nonn
AUTHOR
R. H. Hardin Feb 09 2009
STATUS
approved