Powers of fourth root of 20 rounded up.

Terms

a(0) =1a(1) =3a(2) =5a(3) =10a(4) =20a(5) =43a(6) =90a(7) =190a(8) =400a(9) =846a(10) =1789a(11) =3783a(12) =8000a(13) =16918a(14) =35778a(15) =75660a(16) =160000a(17) =338359a(18) =715542a(19) =1513187a(20) =3200000a(21) =6767177a(22) =14310836a(23) =30263732a(24) =64000000a(25) =135343522a(26) =286216702a(27) =605274630a(28) =1280000000