Number of nonisomorphic semigroups with n elements satisfying the equation xyz = xz.

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =10a(5) =14a(6) =27a(7) =36a(8) =64a(9) =90a(10) =150a(11) =213a(12) =358a(13) =514a(14) =840a(15) =1262a(16) =2038a(17) =3106a(18) =5037a(19) =7805a(20) =12627a(21) =19905a(22) =32189a(23) =51291a(24) =83262a(25) =133756a(26) =217610a(27) =352321a(28) =574994a(29) =936255