Number of nX2 0..3 arrays with row sums equal and column sums equal.

Terms

a(0) =4a(1) =16a(2) =16a(3) =96a(4) =104a(5) =904a(6) =788a(7) =10448a(8) =6280a(9) =134716a(10) =51308a(11) =1853064a(12) =425884a(13) =26527440a(14) =3575216a(15) =389480016a(16) =30269864a(17) =5813357404a(18) =257993708a(19) =87736873196a(20) =2210701460a(22) =19026456248a(24) =164353672604