There is a class of numbers, 9-1 = 8,16-4 = 12,25-9 = 16,36-16 = 20. Q n is a positive integer, which is expressed as -?

There is a class of numbers, 9-1 = 8,16-4 = 12,25-9 = 16,36-16 = 20. Q n is a positive integer, which is expressed as -?

(n+2)²-n²=4(n+1)