SquaresR

SquaresR[d, n] gives the number of ways to represent the integer n as a sum of d squares.

Examples

Number of ways to write 5 as sum of 2 squares:

SquaresR[2, 5]
(* 8 *)

Number of ways to write 10 as sum of 4 squares:

SquaresR[4, 10]
(* 120 *)

Please visit the official Wolfram Language Reference for more details.