About css pseudo-class selector: nth-of-type(n) selector

  html5, question

Who can explain the selector NTH-of-type (4n+1): NTH-of-type (n) in the following picture? ?

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: nth-of-type(n) calculates only certain types of child elements specified in the parent element
“n” is its parameter and can be integer value (1,2,3,4), expression (2n+1, -n+5) and keyword (odd, even), but the starting value of parameter n is always 1, not 0. That is, when the value of parameter n is 0, the selector will not select any matching elements.

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