Instantons on various spaces can be constructed via a generalization of the
Fourier transform called the ADHM-Nahm transform. An explicit use of this
construction, however, involves rather tedious calculations. Here we derive a
simple formula for instantons on a space with one periodic direction. It
simplifies the ADHM-Nahm machinery and can be generalized to other spaces.Comment: AMS-LaTeX, 19 page