COMMENTS

From Mikk Heidemaa, Mar 23 2015: (Start) a(2),...,a(24) all have a single representation (in positive integers) as the sum of two squares (e.g., a(24) = 416865370156^2 + 428846797599^2) and as the hypotenuse of a primitive Pythagorean triple (357686312646216567629137^2 = 10132838975618776700465^2 + 357542758042644694110888^2). --- a^2 + b^2 + c^2 + d^2 + e^2 + f^2 = 357686312646216567629137^2; a=304233682432674451033719; b=185074861663432734470527; c=4189176178164916432878; d=33333333333333333333333; e=3333333; f=3. --- a^2 + b^2 + c^2 + d^2 + e^2 + f^2 = 357686312646216567629137^3; a=210197737649788368191109924028342434; b=39738123500625252940689952285037741; c=777777777777777777777777; d=777777777777777777777777; e=777777777777777777; f=777777777777. a=170350493188466620042802284807886346; b=129394423538599186274382140531063939; c=777777777777777777777777; d=777777777777777777777777; e=777777777777777777; f=777777777777. --- x^2 + y^2 = 357686312646216567629137^3; x=144701758632763782416276428525674993; y=157555096461604743754426503960480452; x=149107037120999813337660002835835372; y=153392629723324670471173010334042063. (End)