Least number of 4th powers needed to represent n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =10a(10) =11a(11) =12a(12) =13a(13) =14a(14) =15a(15) =1a(16) =2a(17) =3a(18) =4a(19) =5a(20) =6a(21) =7a(22) =8a(23) =9a(24) =10a(25) =11a(26) =12a(27) =13a(28) =14a(29) =15