G.f.: Product_{n>0} ( (1+x^n)/(1-x^n) )^(n^2).

Terms

a(0) =1a(1) =2a(2) =10a(3) =36a(4) =118a(5) =376a(6) =1148a(7) =3376a(8) =9654a(9) =26894a(10) =73192a(11) =195188a(12) =510948a(13) =1315048a(14) =3332720a(15) =8326448a(16) =20529526a(17) =49998884a(18) =120379574a(19) =286726340a(20) =676057144a(21) =1578880480a(22) =3654180236a(23) =8385122192a(24) =19085029540a(25) =43103203626a(26) =96630606968a(27) =215105226728a(28) =475608824400