1) the properties of titanium;
2) whether Jesus spoke Aramaic or Hebrew:
3) pentagonal numbers (from Wikipedia; the number of distinct dots in a pattern of dots consisting of the outlines of regular pentagons with sides up to n dots, when the pentagons are overlaid so that they share one vertex).
Examples of Pentagonal NumberThere are 22 distinct dots in the given pentagonal figure. So, 22 is a pentagonal number (from http://www.icoachmath.com/math_dictionary/pentagonal_number.html)
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