a(n) = binomial(sigma(n+1), sigma(n)).

Terms

a(0) =3a(1) =4a(2) =35a(3) =0a(4) =924a(5) =0a(6) =6435a(7) =0a(8) =8568a(9) =0a(10) =30421755a(11) =0a(12) =1961256a(13) =1a(14) =2629575a(15) =0a(16) =62359143990a(17) =0a(18) =513791607420a(19) =0a(20) =58905a(21) =0a(23) =0a(24) =4280561376a(25) =0a(27) =0a(29) =0a(31) =0a(32) =25827165