###GolfScript, 24 characters ###

~:&1.{.2$+&%.2$(|}do](-,

Next iteration of a GolfScript implementation. The second version now also handles 1 correctly. It became quite long but maybe someone can find a way to shorten this version. You can try above version online.

GolfScript, 24 characters

~:&1.{.2$+&%.2$(|}do](-,

Next iteration of a GolfScript implementation. The second version now also handles 1 correctly. It became quite long but maybe someone can find a way to shorten this version. You can try above version online.

###GolfScript, 24 characters ###

~:r;1.{.2$+r%.(2$|}do],(

A first implementation in GolfScript. It became quite long but maybe someone can find a way to shorten this version. You can try above version online.

###GolfScript, 24 characters ###

~:&1.{.2$+&%.2$(|}do](-,

Next iteration of a GolfScript implementation. The second version now also handles 1 correctly. It became quite long but maybe someone can find a way to shorten this version. You can try above version online.