Hi, I used to be a maths teacher but that was years ago and I'm rusty. My question concerns sequences and series. If two simple integer sequences, each with its own nth term formula, are combined, in what conditions can the resulting sequence have its own nth term formula? Here's my example: 1, 4, 3, 8, 5, 12, .... This combines odd numbers and double numbers, the formulas being 2n - 1 and 2n. I've tried and failed to find an nth term formula that works for each term rather than one for the even terms and another for the odd. Any help would be much appreciated.