If n runs through all the positive integers, then f(n) \equal{} \left \lfloor n \plus{} \sqrt {3n} \plus{} \frac {1}{2} \right \rfloor runs through all positive integers skipping the terms of the sequence a_n \equal{} \left \lfloor \frac {n^2 \plus{} 2n}{3} \right \rfloor. floor functionalgebra unsolvedalgebra