Yeah, gseq, which is apparently in the coreutils package.
As I said, geany is in openbsd ports, so it builds there, so either seq is available or configure is being modified by the ports build?
I don't see it's being modified. The maintainer's probably ignoring the output. All seq is used for is printing a bunch of hyphens. As shown in my output above, `configure` completes.
This issue is very trivial and only appearance-related.