@misc{cryptoeprint:2007:096,
author = {R. Wm. Gosper and Rich Schroeppel},
title = {Somos Sequence Near-Addition Formulas and Modular Theta Functions},
howpublished = {Cryptology ePrint Archive, Report 2007/096},
year = {2007},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.