data/problems/42.yml
---
:id: 42
:name: Coded triangle numbers
:url: https://projecteuler.net/problem=42
:content: |+
The _n_<sup>th</sup> term of the sequence of triangle numbers is given by, _t<sub>n</sub>_ = ½_n_(_n_+1); so the first ten triangle numbers are:
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
By converting each letter in a word to a number corresponding to its alphabetical position and adding these values we form a word value. For example, the word value for SKY is 19 + 11 + 25 = 55 = _t_<sub>10</sub>. If the word value is a triangle number then we shall call the word a triangle word.
Using [words.txt](project/resources/p042_words.txt) (right click and 'Save Link/Target As...'), a 16K text file containing nearly two-thousand common English words, how many are triangle words?