Number of different values of i^2 + j^2 + k^2 for i,j,k in [ 0,n ] (or [ -n,n ]).

Terms

a(0) =1a(1) =4a(2) =10a(3) =19a(4) =32a(5) =45a(6) =67a(7) =88a(8) =116a(9) =145a(10) =179a(11) =212a(12) =260a(13) =300a(14) =347a(15) =402a(16) =464a(17) =517a(18) =592a(19) =649a(20) =727a(21) =803a(22) =886a(23) =953a(24) =1057a(25) =1146a(26) =1243a(27) =1343a(28) =1453a(29) =1547