> Related questions: What types of sequences can Perl 6 recognize?
As covered by Jonathan Lang earlier in this thread (though it was
perhaps easy to miss), Perl 6 auto-detects arithmetic sequences (same
additive difference each time) and geometric sequences (same
multiplicative factor applied each time). Two terms are enough to seed
the first kind; three terms are necessary for the second kind.
If you supply three terms that follow neither an arithmetic or a
geometric sequence (and doesn't contain a Callable as its last term),
Perl 6 throws up its hands and doesn't try to guess.
If you ask me, auto-detecting arithmetic and geometric sequences, but
nothing else, is pretty much the sweet spot. We don't want to put more
in CORE. The one that comes up most often as a suggested addition is
the sequence of primes. Mostly just to mess with people who try it.