progressions

Let
Tn = 1 + 2 + 3 + · · · + n and
Pn =T2T2-1.T3T3-1.T4T4-1.......TnTn-1

Find Pn????

2 Answers

1057
Ketan Chandak ·

sorry...
assume n=1991

106
Asish Mahapatra ·

Tn=n(n+1)/2

Tn-1 = (n+2)(n-1)/2

Tn-1 -1 = (n+1)(n-2)/2

TnTn-1 - 1 = nn-2

taking products of terms we get

T2*314253....19911899

= 3*0.5*1990*1991

= 5943135

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