Number of n X n arrays of squares of integers, symmetric under 90 degree rotation, with all rows summing to 3.

A156433

Number of n X n arrays of squares of integers, symmetric under 90 degree rotation, with all rows summing to 3.

Terms

    a(0) =1a(1) =2a(2) =0a(3) =0a(4) =42a(5) =276a(6) =0a(7) =0a(8) =20340a(9) =216680a(10) =0a(11) =0a(12) =30693320a(13) =449345680a(14) =0a(15) =0a(16) =105796267920a(18) =0a(19) =0a(22) =0a(23) =0a(26) =0a(27) =0

External references