oh ok, thanks a lot

For SQL katas, you shouldn't create functions, normally it's just a select statement what you should write:

--# write your SQL statement here:

-- you are given a table 'sumtriangular' with column 'n'

-- return a table with this column and your result in a column named 'res'.

I do not understand how to submit it properly in postgresql. I created a function but sample data does not see it. It is working only if I manually SELECT * FROM function. What should I do?