EditorialThe Fibonacci sequence, in which every term (starting with the 3rd term) is the sum of the two preceding numbers, is one of the more familiar sequences in the On-Line Encyclopedia of Integer Sequences, which first appeared as a handbook in 1973. (Tony Cenicola/The New York Times)
EditorialAlan Canfora holds a CD that contains an audio recording that he said proved the National Guard opened fire on Kent State University students in 1970 not out of panic, but because they were ordered to do so, at a news conference in Kent, Ohio, on Tuesday, May 1, 2007. (David Maxwell/The New York Times)