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A094529 Numbers with at least one arithmetic progression of four divisors (not necessarily consecutive). 3

%I

%S 12,24,36,48,60,72,84,96,105,108,120,132,140,144,156,168,180,192,204,

%T 210,216,228,240,252,264,276,280,288,300,312,315,324,336,348,360,372,

%U 384,396,408,420,432,440,444,456,468,480,492,504,516,525,528,540,552,560

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

%C All multiples of terms are also terms.

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

%H Alois P. Heinz, <a href="/A094529/b094529.txt">Table of n, a(n) for n = 1..10000</a>

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

%Y Cf. A091011, A094530.

%Y See A270571 for another version.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, May 07 2004

%E Edited by _Harvey P. Dale_ and _Alois P. Heinz_, Mar 18 2016

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Last modified September 28 11:24 EDT 2022. Contains 357070 sequences. (Running on oeis4.)