|
%I #5 Dec 18 2015 18:17:18
%S 1,2,24,552,39012,11870808,25684597626,1292153534554332
%N Number of n X n arrays of squares of integers, symmetric about main diagonal, with all rows summing to 81.
%e From Neven Juric, Mar 01 2010: To illustrate a(3) =24:
%e {(0,0,81),(0,81,0),(81,0,0)}
%e {(0,81,0),(81,0,0),(0,0,81)}
%e {(1,16,64),(16,49,16),(64,16,1)}
%e {(1,16,64),(16,64,1),(64,1,16)}
%e {(1,64,16),(64,1,16),(16,16,49)}
%e {(1,64,16),(64,16,1),(16,1,64)}
%e {(9,36,36),(36,9,36),(36,36,9)}
%e {(9,36,36),(36,36,9),(36,9,36)}
%e {(16,1,64),(1,64,16),(64,16,1)}
%e {(16,16,49),(16,49,16),(49,16,16)}
%e {(16,49,16),(49,16,16),(16,16,49)}
%e {(16,64,1),(64,1,16),(1,16,64)}
%e {(36,9,36),(9,36,36),(36,36,9)}
%e {(36,36,9),(36,9,36),(9,36,36)}
%e {(49,16,16),(16,1,64),(16,64,1)},
%e {(49,16,16),(16,16,49),(16,49,16)}
%e {(49,16,16),(16,49,16),(16,16,49)}
%e {(49,16,16),(16,64,1),(16,1,64)}
%e {(64,1,16),(1,16,64),(16,64,1)}
%e {(64,1,16),(1,64,16),(16,16,49)}
%e {(64,16,1),(16,1,64),(1,64,16)}
%e {(64,16,1),(16,49,16),(1,16,64)}
%e {(81,0,0),(0,0,81),(0,81,0)}
%e {(81,0,0),(0,81,0),(0,0,81)}
%K nonn
%O 1,2
%A _R. H. Hardin_ Feb 09 2009
|
