2+6+10+...+(4n-2) = 2n²

P(1):	4n-2 = 2n²
	(4.1)-2 = 2.1²
	4-2=2
	2=2	OK

P(k+1):	2+6+10+(4n-2)+(4(k+1)-2) = 2(k+1)²
	= 2k²+(4(k+1)-2)
	= 2k²+4k+4-2
	= 2k²+4k+2
	= 2(k²+2k+1)
	= 2(k+1)²