I want to know the nth term of tibonacci series, given by the recurrence relation
$$
a\_{n + 3} = a\_{n + 2} + a\_{n + 1} + a\_n
$$
with $a\_1 = 1, a\_2 = 2, a\_3 = 4$, so the first few terms are
$$
1,2,4,7,13,24,44, \ldots
$$
I am more interested in derivation of how the nth term is calculated rather than direct comming up with black box formula.