G.f. A(x) satisfies A(x) = 1 / (1 - x * A(x^4)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =4a(8) =5a(9) =7a(10) =10a(11) =14a(12) =19a(13) =26a(14) =36a(15) =50a(16) =69a(17) =95a(18) =131a(19) =181a(20) =250a(21) =346a(22) =478a(23) =660a(24) =911a(25) =1259a(26) =1740a(27) =2404a(28) =3320a(29) =4586