G.f. 1/[Sum_{n>=0} (2*n+1)*(-x)^(n*(n+1)/2)].

Terms

a(0) =1a(1) =3a(2) =9a(3) =32a(4) =111a(5) =378a(6) =1287a(7) =4395a(8) =15012a(9) =51247a(10) =174930a(11) =597177a(12) =2038676a(13) =6959625a(14) =23758677a(15) =81107291a(16) =276883938a(17) =945225504a(18) =3226807479a(19) =11015664750a(20) =37605240819a(21) =128376648392a(22) =438251781660