Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 2.

A156430

Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 2.

Terms

    a(0) =1a(1) =2a(2) =10a(3) =12a(4) =84a(5) =132a(6) =954a(7) =1728a(8) =13290a(9) =26820a(10) =217500a(11) =481320a(12) =4086600a(13) =9783480a(14) =86549820a(15) =221921280a(16) =2037627900a(17) =5552479800a(18) =52745205240a(19) =151802154000

External references