x are forma 4*n+1 unde n este nr nat
Deci,
1+5+9+...+(4*n+1)=
=(4*0+1)+(4*1+1)+(4*2+1)+...+(4*n+1)=
=4*(0+1+2+...+n)+1+1+...+1=
=4*(0+1+2+...+n)+(n+1)=
=(4*n*(n+1)/2)+(n+1)=2*n*(n+1)+(n+1)=
=(n+1)*(2*n+1)
dar cum relatia era egala cu 231,
(n+1)(2*n+1)=231ec de gr 2
dar are solutie unica, pt delta va fi 0
n=10
x=4*n+1=41
