Tuesday, November 09, 2004
Encyclopedia of Integer Sequences
The answer is 21, and this sequence is known as the Fibonacci sequence. Each term is the sum of the previous two terms.
There is an entire encyclopedia of sequences like this, the Encyclopedia of Integer Sequences, which recently passed the 100,000 entry mark. Started by mathematician Neil J. A. Sloane in 1963 on punched cards, the Encyclopedia is now a major research tool and collaborative database.
Here are some sequences contributed by yours truly:A069283.