First differences of A109033.

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =16a(5) =66a(6) =280a(7) =1216a(8) =5384a(9) =24224a(10) =110464a(11) =509480a(12) =2372704a(13) =11142656a(14) =52709600a(15) =250933120a(16) =1201354240a(17) =5780413760a(18) =27937867520a(19) =135574988800a(20) =660314620160