1,2+3,4+5+6,7+8+9+10…… The general term formula of

1,2+3,4+5+6,7+8+9+10…… The general term formula of

The number of the nth line is: 1 / 2n (n-1) + 1,1 / 2n (n-1) + 2 ,1/2n(n+1)