Minimal possible denominator for a sum of the form 1 +/- 1/2 +/- 1/3 +/- ... +/- 1/n.

Terms

a(0) =1a(1) =2a(2) =6a(3) =12a(4) =60a(5) =20a(6) =140a(7) =280a(8) =2520a(9) =2520a(10) =27720a(11) =27720a(12) =360360a(13) =360360a(14) =72072a(15) =144144a(16) =2450448a(17) =272272a(18) =5173168a(19) =5173168a(20) =739024a(21) =739024a(22) =16997552a(23) =16997552a(24) =424938800a(25) =424938800a(26) =11473347600a(27) =11473347600a(28) =332727080400a(29) =332727080400