Number of strongly asymmetric sequences of length n.

Terms

a(0) =4a(1) =12a(2) =36a(3) =96a(4) =264a(5) =648a(6) =1584a(7) =3576a(8) =7872a(9) =15360a(10) =29184a(11) =51120a(12) =90384a(13) =158448a(14) =286296a(15) =509808a(16) =904296a(17) =1556304a(18) =2638368a(19) =4273512a(20) =6783888a(21) =10308576a(22) =15419640a(23) =22305840a(24) =32204568a(25) =45812088a(26) =65912784a(27) =94069080