Odd Catalan numbers
Number Theory
Level
5
The Catalan numbers are defined by the formula \[ C_n = \frac1{n+1}\binom{2n}{n}. \] How many \( n \) are there such that \( 1{,}000 \le n \le 100{,}000\) and \( C_n \) is odd?
by
Patrick Corn