Number of 4-matchings of the n X n grid graph.

Terms

a(0) =0a(1) =0a(2) =0a(3) =18a(4) =2593a(5) =39979a(6) =281514a(7) =1301950a(8) =4618099a(9) =13628193a(10) =35115244a(11) =81502564a(12) =174076485a(13) =347418199a(14) =655313518a(15) =1178436234a(16) =2034127639a(17) =3388621645a(18) =5472091824a(19) =8596923568a(20) =13179641449a(21) =19766948739a(22) =29066362930a(23) =41981957974a(24) =59655750843a(25) =83515296889