Prove that every even integer n with 2 ≤ n ≤ 26 can be written as a sum of at most three perfect square

Question

Sorry to say. Completely I dont know about this question. I have searched in google I could not find answer . Can anyone say about this.

Answer 1

• $ 2=1+1$
• $ 4=4$
• $ 6=4+1+1$
• $ 8=4+4$
• $10=9+1$
• $12=4+4+4$
• $14=9+4+1$
• $16=16$
• $18=16+1+1$
• $20=16+4$
• $22=9+9+4$
• $24=16+4+4$
• $26=16+9+1$