 The problem has, however, also been extended to even values of formula_6 by asking, for those formula_6, whether all of the edges of the complete graph except for a perfect matching can be covered by copies of the given 2-regular graph.Like the ménage problem (a different mathematical problem involving seating arrangements of diners and tables), this variant of the problem can be formulated by supposing that the formula_6 diners are arranged into formula_12 married couples, and that the seating arrangements should place each diner next to each other diner except their own spouse exactly once.The only instances of the Oberwolfach problem that are known not to be solvable are formula_13, formula_14, formula_15, and formula_16.