An explicit formula for the number of solutions of X^2=0 in triangular matrices over GF(q) (To appear in Elec. J. Comb.)

Some problems are impossible to resist. For me, any problem that contains recurrences or q- are irresistible. If they contain both, then I am really hooked. That's what happened when Sasha Kirillov told me about the problem described and solved in this paper.