marxen.c is an entry by Heiner Marxen for the Bignum Bakeoff contest, whose objective is to write a C program (in 512 characters or less) that generates the largest possible output. It came in second place in the competition, behind Loader's number. The program uses a variant of the Goodstein sequence. Its output is lower bounded by \(f_{\omega^{\omega}}(2\uparrow\uparrow 500)\) and upper bounded by \(f_{\varepsilon_{0}+{\omega^3}}(1000000)\) in the fast-growing hierarchy.