4.5       4
  5.5      20
  6.5      50
  7.5     126
  8.5     321
  9.5     844
 10.5    2107
 11.5    5073
 12.5   11803
 13.5   26177
 14.5   56575
 15.5  116670
 16.5  226765
 17.5  419925
 18.5  731159
 19.5 1181214