@MartinSleziak I don't quite understand the tag creator's argument – what material difference does it make to a question, whether or not OEIS is referenced? And "but it is not possible to unite these questions except with a tag since the A number is not known in advance (and the question doesn't always write OEIS..." is rather weak, since searching [oeis] oeis is:question returns 11 of the 13 questions currently tagged (oeis). — epimorphic 20 mins ago