sir,please suggest a standard formula for calculating the sum of first n perfect squares

that is 1+4+9+..................................n=?

formula is n(n+1)(2n+1)\6

thank very much sir i am obligue to you

is it derived by writing 1+4+9+16......................................n=1+1+3+1+3+5+1+3+5+7........................................n.

if it does not bother you please explain