Pretty sure it was Hoftstadter (in his Metamagical Themas column; note that the title is an anagram of Gardner’s Mathematical Games) rather than Gardner. You can find the relevant columns, and some further discussion, in his book of that title.
Thanks! I’ve read the book, a decade ago, so I’m fairly sure that what I was mis-remembering.
Pretty sure it was Hoftstadter (in his Metamagical Themas column; note that the title is an anagram of Gardner’s Mathematical Games) rather than Gardner. You can find the relevant columns, and some further discussion, in his book of that title.
Thanks! I’ve read the book, a decade ago, so I’m fairly sure that what I was mis-remembering.