Number of n X n arrays of squares of integers, symmetric under 90-degree rotation, with all rows summing to 2.

A156431

Number of n X n arrays of squares of integers, symmetric under 90-degree rotation, with all rows summing to 2.

Terms

    a(0) =1a(1) =0a(2) =2a(3) =0a(4) =12a(5) =0a(6) =90a(7) =0a(8) =810a(9) =0a(10) =8940a(11) =0a(12) =116760a(13) =0a(14) =1756860a(15) =0a(16) =29933820a(17) =0a(18) =569744280a(19) =0a(20) =11981526480a(21) =0a(22) =275893362360a(23) =0a(25) =0a(27) =0

External references