a(n) = 2^n * [x^n] Product_{k>=1} (1 + 2*x^k)^(1/2).

Terms

a(0) =1a(1) =2a(2) =2a(3) =20a(4) =6a(5) =108a(6) =148a(7) =776a(8) =-186a(9) =5964a(10) =-4a(11) =51032a(12) =-89700a(13) =512120a(14) =-1259416a(15) =6406032a(16) =-19733434a(17) =78363148a(18) =-268823572a(19) =1047941688a(20) =-3800035916a(21) =14327505832a(22) =-52766730600a(23) =199492430192a(24) =-746479735524