When is the sum of two squares a cube?

 
 

2^2 \; + \; 2^2 \; = \; 2^3

2^2 \; + \; 11^2 \; = \; 5^3

18^2 \; + \; 26^2 \; = \; 10^3

52^2 \; + \; 47^2 \; = \; 17^3

110^2 \; + \; 74^2 \; = \; 26^3

198^2 \; + \; 107^2 \; = \; 37^3

322^2 \; + \; 146^2 \; = \; 50^3

488^2 \; + \; 191^2 \; = \; 65^3

702^2 \; + \; 242^2 \; = \; 82^3

970^2 \; + \; 299^2 \; = \; 101^3

1298^2 \; + \; 362^2 \; = \; 122^3

1692^2 \; + \; 431^2 \; = \; 145^3

2158^2 \; + \; 506^2 \; = \; 170^3

2702^2 \; + \; 587^2 \; = \; 197^3

3330^2 \; + \; 674^2 \; = \; 226^3

4048^2 \; + \; 767^2 \; = \; 257^3

4862^2 \; + \; 866^2 \; = \; 290^3

5778^2 \; + \; 971^2 \; = \; 325^3

6802^2 \; + \; 1082^2 \; = \; 362^3

7940^2 \; + \; 1199^2 \; = \; 401^3

 

(a^2 + b^2)^2 \; = \; (a^2 - b^2)^2 \; + \; (2 \, a \, b)^2

multiplying both sides by   (a^2 + b^2)

(a^2 + b^2)^3 \; = \; (a^3 - 3 \, a \, b^2)^2 \; + \; (3 \, a^2 \, b - b^3)^2

 
 
 
 
 
 
 
 
 
 
 
 
 

About benvitalis

math grad - Interest: Number theory
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2 Responses to When is the sum of two squares a cube?

  1. pipo says:

    Nice, sequence is:

    (n^2+1)^3 = (n^3 -3n)^2 + (3n^2-1)^2

    pipo

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