Powers of cube root of 20 rounded down.

Terms

a(0) =1a(1) =2a(2) =7a(3) =20a(4) =54a(5) =147a(6) =400a(7) =1085a(8) =2947a(9) =8000a(10) =21715a(11) =58944a(12) =160000a(13) =434306a(14) =1178890a(15) =3200000a(16) =8686136a(17) =23577801a(18) =64000000a(19) =173722727a(20) =471556031a(21) =1280000000a(22) =3474454549a(23) =9431120636a(24) =25600000000a(25) =69489090984a(26) =188622412730a(27) =512000000000