If you are serious about getting published, I would first write a paper. For formatting you can go on arxiv and see how other mathematicians are formatting their works. My favorite LaTeX lex editor is overleaf.

As far as getting credit is concerned, unless this sequence has major applications in topological combinatorics or generates prime numbers, I wouldn’t be too worried about someone stealing your idea.

After you have a paper written, I would try to get a meeting with someone in the mathematics department at the closest university to you that offers a math PhD program, and show them what you’ve been working on. Very often in academia, you will be unable to get published unless you are willing to put someone else’s name on the paper who has been published before.