According to Mathworld a mathematical constant is any well-defined real number which is significantly interesting in some way.
Here is an article about set of new constants. https://oeis.org/wiki/Convergents_constant
i found this in unanswered posts and didn't want it to go to waste!
Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment