a(n) = floor( Pi^(n/3) ).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =6a(5) =9a(6) =14a(7) =21a(8) =31a(9) =45a(10) =66a(11) =97a(12) =142a(13) =208a(14) =306a(15) =448a(16) =656a(17) =961a(18) =1408a(19) =2062a(20) =3020a(21) =4423a(22) =6478a(23) =9488a(24) =13896a(25) =20353a(26) =29809a(27) =43658a(28) =63941a(29) =93648