Within `sagemath`, you can
access Guess as `fricas.guess([1,2,5,14,42])` (after doing "`sage -i fricas`"
on the command line, to install FriCAS). Within FriCAS, you have more
options, in particular you can try to express consecutive ratios or
differences as functions of the form `(a + b n)^n r(n)`, where `r` is a
rational function.

Christian Krattenthaler