Sigma lens 35-80mm - need adapter?

I have an old pentax that I've only just realized has a detachable SIGMA 35-80mm lens. I have recently bought a NIKON D3100, and I was wondering is there like an adapter or a mount I can put the lens in, to be able it on my Nikon?

You can certainly buy a Pentax K/Nikon adapter, but the optical compromise on an already mediocre lens may not be worth it.

You'll lose both autofocus and metering, and the lens will do little that your 18-55mm can't do far better.