A094529 Numbers with at least one arithmetic progression of four divisors (not necessarily consecutive).

12, 24, 36, 48, 60, 72, 84, 96, 105, 108, 120, 132, 140, 144, 156, 168, 180, 192, 204, 210, 216, 228, 240, 252, 264, 276, 280, 288, 300, 312, 315, 324, 336, 348, 360, 372, 384, 396, 408, 420, 432, 440, 444, 456, 468, 480, 492, 504, 516, 525, 528, 540, 552, 560

Offset: 1

Author

Reinhard Zumkeller, May 07 2004

Keywords

• nonn

Comments

All multiples of terms are also terms.

a(n) = m*A094530(k) for appropriate m and k.

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A091011, A094530.

See A270571 for another version.

Programs

Mathematica

sd4Q[n_]:=Count[Subsets[Divisors[n],{4}],?(Length[Union[ Differences[ #]]] == 1&)]>0; Select[Range[600],sd4Q] (* _Harvey P. Dale, Mar 19 2016 *)

Extensions

Edited by Harvey P. Dale and Alois P. Heinz, Mar 18 2016