# Summing an arithmetic sequence

This post is to test how Latex output from Mathematica appears via MathJax. It also shows a handy way to sum up a sequence of numbers that have the same difference between them.

Suppose you have a series of numbers that start with a number we call a. If the next number, and the ones after it, in the sequence differ by the same value, then the formula given below can be used to calculate the number of items in the sequence:

$$n=frac{L-a}{d}+1$$

where a = the first term in the sequence, L = the last term in the sequence, and d = difference between the terms in the sequence. d has to be non-zero and the same between each set of terms in the sequence.

Once you know the number of terms in an arithmetic sequence you can sum the terms using the formula: $$S=frac{1}{2} n (2 a+ (n-1)d)$$, where a = the first term in the sequence, n= the number of terms in the sequence, and d = difference between the terms in the sequence.

The embedded equations above show that the latex from Mathematica does work. Happy days. That’s both Mathematica and MathType I can use as required.