a(n) is the number of configurations of n indistinguishable pairs placed on the vertices of the ladder graph P_2 X P_n such that all but two such pairs are joined by an edge.

A318267

a(n) is the number of configurations of n indistinguishable pairs placed on the vertices of the ladder graph P_2 X P_n such that all but two such pairs are joined by an edge.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =8a(4) =39a(5) =138a(6) =414a(7) =1104a(8) =2715a(9) =6282a(10) =13875a(11) =29540a(12) =61060a(13) =123192a(14) =243589a(15) =473540a(16) =907335a(17) =1716974a(18) =3214066a(19) =5959704a(20) =10958687a(21) =20001526a(22) =36264579a(23) =65359752a(24) =117165096a(25) =209008464a(26) =371190217a(27) =656540768a(28) =1156924167a(29) =2031676818

External references