A001147 with each term repeated.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =3a(6) =15a(7) =15a(8) =105a(9) =105a(10) =945a(11) =945a(12) =10395a(13) =10395a(14) =135135a(15) =135135a(16) =2027025a(17) =2027025a(18) =34459425a(19) =34459425a(20) =654729075a(21) =654729075a(22) =13749310575a(23) =13749310575a(24) =316234143225a(25) =316234143225