Are all triangular numbers odd

Answer 1

7 of the first 15 triangular numbers (462/3 percent) are even.

1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120 ...

From this fragment of the series, it sure begins to look as if every second pair

of triangular numbers are both even, and that 50% of all of them are.