a(n) equals the coefficient of x^n in f(x)^n where f(x)=1+sum(n>=0,x^(2^n)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =23a(5) =71a(6) =231a(7) =743a(8) =2431a(9) =7999a(10) =26563a(11) =88683a(12) =297551a(13) =1002015a(14) =3385175a(15) =11466887a(16) =38933183a(17) =132454719a(18) =451423203a(19) =1540920939a(20) =5267257103a(21) =18027478847a(22) =61770328227a(23) =211872505243a(24) =727411948351