Number of ways to place 2 nonattacking bishops on an n X n board.

Terms

a(0) =0a(1) =4a(2) =26a(3) =92a(4) =240a(5) =520a(6) =994a(7) =1736a(8) =2832a(9) =4380a(10) =6490a(11) =9284a(12) =12896a(13) =17472a(14) =23170a(15) =30160a(16) =38624a(17) =48756a(18) =60762a(19) =74860a(20) =91280a(21) =110264a(22) =132066a(23) =156952a(24) =185200a(25) =217100a(26) =252954a(27) =293076a(28) =337792a(29) =387440