L.g.f.: log(1 + 2*Sum_{n>=1} 2^n * x^(n^2)).

Terms

a(0) =4a(1) =-16a(2) =64a(3) =-224a(4) =864a(5) =-3328a(6) =12800a(7) =-49408a(8) =190864a(9) =-736896a(10) =2845440a(11) =-10987520a(12) =42426752a(13) =-163825664a(14) =632592384a(15) =-2442673664a(16) =9432071040a(17) =-36420732160a(18) =140633977856a(19) =-543040041984