Floor(n^(1/4) * sqrt(log(n))).
0, 0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6
1
This formula, without the floor function, appears in the paper by Hittmeir.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
Markus Hittmeir, Deterministic factorization of sums and differences of powers, arXiv 1512.06401 (Dec 20 2015)
(Mma) Table[Floor[n^(1/4) Sqrt[Log[n]]], {n, 100}]
nonn
T. D. Noe, Dec 22 2015