A094529 - OEIS

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

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OFFSET

1,1

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

MATHEMATICA

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

CROSSREFS

Cf. A091011, A094530.