What is the sum of √ 2 + √ 4 + √ 8 + √ 16 + √ 32 + √ 64 + √ 128 + ... up to 20 terms ?
What is the sum of 1 -LRB- / √ 2 -RRB- + -LRB- 1 / √ 4 -RRB- + -LRB- 1 / √ 8 -RRB- + -LRB- 1 / √ 16 -RRB- + -LRB- 1 √ 32 -RRB- + -LRB- 1 / √ 64 -RRB- + -LRB- 1 / √ 128 -RRB- + -LRB- 1 / √ 256 -RRB- ... up to 20 terms ?