A047104 T(n,n-2), array T as in A047100.
1, 2, 5, 21, 89, 340, 1312, 5106, 19782, 76676, 297776, 1157609, 4505193, 17554888, 68480902, 267420957, 1045329995, 4089922224, 16015961548, 62768643959, 246184737835, 966243694608, 3794894344275, 14913585439328
Offset: 2