I remember having read a long and detailed article somewhere about the practice of writing out certain words and phrases using nothing but numbers (893 for ヤクザ, 39 for サンキュー, etc.), as well as "transcribing" longer phrases with a string of numbers as a riddle, challenging others to figure out what phrase the numbers stand for. The article had lots of examples of such usage, as well as a table demonstrating the correspondence between individual numbers and syllables/morae they may replace. I'm 95% certain that the article in question was on the English Wikipedia. The problem is I can't find it anywhere - the Japanese numerals article neither mentions this practice nor links to an article about it, and I've tried searching for it by typing in various possible keywords, both on Wikipedia and on Google, to no avail. Does anybody know the proper term for this, in Japanese or in English? Or maybe someone here knows of any articles about it? Any help would be appreciated.