Denominators of triangle related to enumeration of minimal 2-covers of a labeled n-set.

Terms

a(0) =1a(1) =3a(2) =3a(3) =7a(4) =2a(5) =7a(6) =15a(7) =5a(8) =21a(9) =15a(10) =31a(11) =3a(12) =651a(13) =186a(14) =31a(15) =63a(16) =7a(17) =651a(18) =651a(19) =651a(20) =63a(21) =127a(22) =4a(23) =11811a(24) =15748a(25) =11811a(26) =762a(27) =127a(28) =255a(29) =9