Squarefree numbers having at least three prime factors that are in arithmetic progression.
105, 231, 627, 897, 935, 1581, 1729, 2465, 2967, 4123, 4301, 4715, 5487, 7685, 7881, 9717, 10707, 11339, 14993, 16377, 17353, 20213, 20915, 21505, 23779, 25327, 26331, 26765, 29341, 29607, 32021, 33335, 40587, 40807, 42911, 48635, 49321, 54739, 55581
1
The first number having four prime factors is 21505 = 5 * 11 * 17 * 23. The first number having five prime factors is 623645 = 5 * 11 * 17 * 23 * 29. See S000920 numbers with two or more prime factors.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
Eric W. Weisstein, MathWorld: Arithmetic Progression
(Mma) t = {}; Do[f = FactorInteger[n]; If[Length[f] > 2 && Union[Transpose[f][[2]]] == {1} && Length[Union[Differences[Transpose[f][[1]]]]] == 1, AppendTo[t, n]], {n, 1, 100000, 2}]; t
nonn
T. D. Noe, Jul 12 2016