  Until 1973 there was no database of integer sequences. Someone coming across
the sequence 1, 2, 4, 9, 21, 51, 127,... would have had no way of discovering
that it had been studied since 1870 (today these are called the Motzkin
numbers, and form entry A001006 in the database). Everything changed in 1973
with the publication of "A Handbook of Integer Sequences", which listed 2372
entries. This report describes the fifty-year evolution of the database from
the "Handbook" to its present form as "The On-Line Encyclopedia of Integer
Sequences" (or OEIS), which contains 360,000 entries, receives a million visits
a day, and has been cited 10,000 times, often with a comment saying "discovered
thanks to the OEIS".
