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

1,2

LINKS

Table of n, a(n) for n=1..8.

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 * A170904 A090732 A014298

Adjacent sequences:  A156522 A156523 A156524 * A156526 A156527 A156528

KEYWORD

nonn

AUTHOR

R. H. Hardin Feb 09 2009

STATUS

approved

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Last modified November 14 07:07 EST 2019. Contains 329110 sequences. (Running on oeis4.)