Question

what's the rule of this sequence:

1-3+5-7+9-11+...+201

Answer 1

\[\sum_{k=1}^{101}(-1)^{k+1}(2k-1)\]

Answer 2

sequence is with commas,
\[1,-3,5,-7,...,201\] series with plus signs
\[1-3+5-7+...+201\]

Answer 3

thanks !