Why sigma n = n -LRB- n +1 -RRB- / 2 not n ^ 2 ?
Why does -LSB- math -RSB- \ lim _ -LCB- n \ to \ infty -RCB- \ frac -LCB- 2 ^ n -RCB- -LCB- 3 ^ -LCB- n +1 -RCB- -RCB- -LSB- / math -RSB- converge to -LSB- math -RSB- \ frac -LCB- 2 -RCB- -LCB- 3 -RCB- -LSB- / math -RSB- ?