Question 978078
{{{1=1^2}}}
{{{9=3^2=(1+2)^2}}}
{{{36=6^2=(3+3)^2}}}
{{{100=10^2=(6+4)^2}}}
{{{225=15^2=(10+5)^2}}}
The next number is {{{(15+6)^2=21^2=441}}}