5^n表示为两个平方和：5^n=x^2+y^2，0<=x<y。
n=0,1，…的解数：a（n）=1,1,2,2,3,3,4,4,5,5,6,6，。。。
n=0,1，…的解的三角形：
{x，y}
{{0,1}},
{{1,2}},
{{0,5},{3,4}},
{{2,11},{5,10}},
{{0,25},{7,24},{15,20}},
{{10,55},{25,50},{38,41}},
{{0,125},{35,120},{44,117},{75,100}},
{{29,278},{50,275},{125,250},{190,205}},
{{0,625},{175,600},{220,585},{336,527},{375,500}},
{{145,1390},{250,1375},{625,1250},{718,1199},{950,1025}},
{{0,3125},{237,3116},{875,3000},{1100,2925},{1680,2635},{1875,2500}},
{{725,6950},{1250,6875},{2642,6469},{3125,6250},{3590,5995},{4750,5125}},
{{0,15625},{1185,15580},{4375,15000},{5500,14625},{8400,13175},{9375,12500},{10296,11753}}
