Pseudocode in Scientific Article In mathematical scientific papers, which section would I detail pseudo code or sample source code? Would that be included in an Appendices section or above under Methods?
How long is it?


If short put it in the paper
If long put it in the appendix

Can your paper stand with-out it? 


If so, then it is supplementary, so goes with the supplementary materials, i.e. in the appendix
If not, then it needs to be in the paper.



If it is both Long and Required, then perhaps you are writing overly detailed pseudocode. I know the formal pseudocode I learnt in high school was detailed to the point of being executable -- which defeats the purpose of pseudo-code -- if it can be written clearly in a language that is in common use in your area (E.g. R for statisticians, Matlab for signals engineers) you can just write it in that language and avoid any ambiguity.

If on the other hand it is short and not required, it can go anywhere (Possibly even in a footnote). Though its still not required.

A common pattern, I've seen a few times is to have pseudocode, or just textual descriptions of the algorithm in the main text. Then an implementation in a real programming language in an appendix; And/Or a footnote linking to the authors website/github where it can be downloaded