a(n) = floor(1/{(n^4+2*n)^(1/4)}), where {}=fractional part.

Terms

a(0) =3a(1) =8a(2) =18a(3) =32a(4) =50a(5) =72a(6) =98a(7) =128a(8) =162a(9) =200a(10) =242a(11) =288a(12) =338a(13) =392a(14) =450a(15) =512a(16) =578a(17) =648a(18) =722a(19) =800a(20) =882a(21) =968a(22) =1058a(23) =1152a(24) =1250a(25) =1352a(26) =1458a(27) =1568a(28) =1682a(29) =1800