The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984 as Sūji wa dokushin ni kagiru (数字は独身に限る?), which also can be translated as "the digits must be single" or "the digits are limited to one occurrence" (In Japanese, dokushin means an "unmarried person"). At a later date, the name was abbreviated to Sudoku (数独) by Maki Kaji (鍜治 真起 Kaji Maki?), taking only the first kanji of compound words to form a shorter version.[10] "Sudoku" is a registered trademark in Japan and the puzzle is generally referred to as Number Place (ナンバープレース Nanbāpurēsu?) or, more informally, a portmanteau of the two words, Num(ber) Pla(ce) (ナンプレ Nanpure?). In 1986, Nikoli introduced two innovations: the number of givens was restricted to no more than 32, and puzzles became "symmetrical" (meaning the givens were distributed in rotationally symmetric cells). It is now published in mainstream Japanese periodicals, such as the Asahi Shimbun. The Times of London began featuring Sudoku in late 2004 after a successful appearance in a local US newspaper, from the efforts of Wayne Gould, and rapidly spread to other newspapers as a regular feature. Gould devised a computer program to produce unique puzzles rapidly.
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