a(n) = [x^n] Product_{k=1..n} 1/(1 + x^k)^(n-k+1).

Terms

a(0) =1a(1) =-1a(2) =2a(3) =-5a(4) =18a(5) =-60a(6) =189a(7) =-601a(8) =1967a(9) =-6544a(10) =21872a(11) =-73247a(12) =246080a(13) =-829924a(14) =2808357a(15) =-9527485a(16) =32389671a(17) =-110316862a(18) =376372802a(19) =-1286063899a(20) =4400499380a(21) =-15075608840a(22) =51704898623a(23) =-177513230200a(24) =610007283817