Also wanted more algebraic like wolfram alpha capability though.
Somehow reminds me http://strlen.com/treesheets/
I was also impressed by the creative approach to the centuries-old task.
Source code: http://bazaar.launchpad.net/~nasc-team/nasc/trunk/files/74
It should be noted that this kind of thing has been available in Mathematica, ipython etc. for literally decades.
Not that the tool is not great, it is.
Other than that, looks like you'll need bzr to pull/clone.