a(n) = denominator of Sum_{i=1..n} 1/A031216(i).

Terms

a(0) =2a(1) =6a(2) =30a(3) =210a(4) =420a(5) =420a(6) =1260a(7) =126a(8) =3150a(9) =97650a(10) =830025a(11) =6640200a(12) =6640200a(13) =312089400a(14) =312089400a(15) =9050592600a(16) =72404740800