Second line of 5-wave sequence A038201.

Terms

a(0) =1a(1) =4a(2) =9a(3) =50a(4) =105a(5) =616a(6) =1287a(7) =7601a(8) =15873a(9) =93819a(10) =195910a(11) =1158052a(12) =2418195a(13) =14294449a(14) =29849041a(15) =176444054a(16) =368442700a(17) =2177943781a(18) =4547886208a(19) =26883530748a(20) =56137003923a(21) =331837870408a(22) =692929213991