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Number of n X n 0..2 symmetric arrays with every row summing to n.
0

%I #9 Apr 08 2020 01:57:09

%S 1,1,3,13,169,5673,526443,133721189,95133854529,190409704025737,

%T 1081810465812816481,17533275809917986947451,

%U 814583187343481957681992873,108889213625061640897043875544377,42017261328544343771207789776696995237,46930798910194830781686389018692804741926963

%N Number of n X n 0..2 symmetric arrays with every row summing to n.

%e Some solutions for n=4

%e ..0..2..2..0....2..2..0..0....2..1..0..1....1..1..0..2....1..2..0..1

%e ..2..0..0..2....2..1..1..0....1..1..2..0....1..2..1..0....2..1..0..1

%e ..2..0..1..1....0..1..1..2....0..2..1..1....0..1..1..2....0..0..2..2

%e ..0..2..1..1....0..0..2..2....1..0..1..2....2..0..2..0....1..1..2..0

%Y Column 2 of A213800.

%K nonn

%O 0,3

%A _R. H. Hardin_, Jun 20 2012

%E a(0)=1 prepended and terms a(10) and beyond from _Andrew Howroyd_, Apr 07 2020