A member of an

integer sequence defined similarly to the

Fibonacci numbers, except that each

term equals the sum of the previous three terms in the series. The first few terms are thus 1, 1, 2, 4, 7, 13, 24, 44, and 81. The ratio between successive terms converges to approximately 1.83928675521416113255..., which is a root of the polynomial

*x*^{3} -x^{2} -x^{2} -1.

I don't recall the name of the teenage mathematician who named this sequence, but I never forget reading that he died in a motorcycle accident before celebrating his sixth Tribonacci birthday.