Number of minimal unavoidable n-celled pebbling configurations.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =4a(5) =22a(6) =98a(7) =412a(8) =1700a(9) =6974a(10) =28576a(11) =117146a(12) =480722a(13) =1974914a(14) =8122084a(15) =33435390a(16) =137757480a(17) =567998152a(18) =2343472004a(19) =9674252070a(20) =39956606552a(21) =165099840920a(22) =682446679582