根据规律填空:(1)4,7,10,+13``````,那么第20项是() (2)1,5,9,13,``````,那么第n项是()(3)12,34,5,6,78,9,10,11,12,13,14,15``````按此规律,可知第n行有( )个正整数.

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根据规律填空:(1)4,7,10,+13``````,那么第20项是()(2)1,5,9,13,``````,那么第n项是()(3)12,34,5,6,78,9,10,11,12,13,14,15``

根据规律填空:(1)4,7,10,+13``````,那么第20项是() (2)1,5,9,13,``````,那么第n项是()(3)12,34,5,6,78,9,10,11,12,13,14,15``````按此规律,可知第n行有( )个正整数.
根据规律填空:(1)4,7,10,+13``````,那么第20项是() (2)1,5,9,13,``````,那么第n项是()
(3)
1
2,3
4,5,6,7
8,9,10,11,12,13,14,15
``````
按此规律,可知第n行有( )个正整数.

根据规律填空:(1)4,7,10,+13``````,那么第20项是() (2)1,5,9,13,``````,那么第n项是()(3)12,34,5,6,78,9,10,11,12,13,14,15``````按此规律,可知第n行有( )个正整数.
(1)规律为3n+1 所以第20项是(61)
(2)规律为4n-3 所以第n项是(4n-3)
(3)规律为2的(n-1)次方,所以第n行有(2的(n-1)次方)个正整数.