Number of ways to arrange 4 nonattacking triangular rooks on an nXnXn triangular grid.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =18a(6) =233a(7) =1449a(8) =6213a(9) =20993a(10) =59943a(11) =150903a(12) =344323a(13) =726033a(14) =1434678a(15) =2685046a(16) =4798206a(17) =8240022a(18) =13669026a(19) =21995586a(20) =34453386a(21) =52685556a(22) =78846471a(23) =115721991a(24) =166869131a(25) =236778399a(26) =331059729a(27) =456655745a(28) =622083189a(29) =837706779