When the Handbook of Integer Sequences came out in 1973, Philip Morrison gave it an enthusiastic review in Scientific American and Martin Gardner was kind enough to say in his "Mathematical Games" column for July 1974 that "every recreational mathemati-cian should buy a copy forthwith." That book contained 2,372 sequences. Today the On-Line Encyclopedia of Integer Sequences (or OEIS) [25] contains over 140,000 sequences. The following are seven that I find especially interesting. Many of them quite literally stagger. The sequences will be labeled with their numbers (such as A064413) in the OEIS. Much more information about them can be found there and in the references cited.
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