Number of 2-matchings of the n-th centered square grid graph.

Terms

a(0) =0a(1) =0a(2) =86a(3) =544a(4) =1854a(5) =4688a(6) =9910a(7) =18576a(8) =31934a(9) =51424a(10) =78678a(11) =115520a(12) =163966a(13) =226224a(14) =304694a(15) =401968a(16) =520830a(17) =664256a(18) =835414a(19) =1037664a(20) =1274558a(21) =1549840a(22) =1867446a(23) =2231504a(24) =2646334a(25) =3116448a(26) =3646550a(27) =4241536a(28) =4906494a(29) =5646704