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A067131
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Number of elements in the largest set of divisors of n which are in arithmetic progression.
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2
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1, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 4, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 4, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 4, 2, 2, 2, 3, 2, 3, 2, 2, 3, 2, 2, 4, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 6, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 4, 2, 2, 3, 2, 2, 3, 2, 3, 2, 2, 2, 4, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 3, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| a(12) = 4 as the divisors of 12 are {1,2,3,4,6,12} and the maximal subset in arithmetic progression is {1,2,3,4}. a(15) = 3; the maximal set is {1,3,5}.
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MATHEMATICA
| lap[s_] := Module[{}, l=Length[s]; If[l<2, Return[l]]; val=2; For[i=1, i<l, i++, For[j=i+1, j<=l, j++, For[k=2, MemberQ[s, k*s[[j]]-(k-1)s[[i]]], k++, Null]; If[k>val, val=k]]]; val]; lap/@Divisors/@Range[1, 200]
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CROSSREFS
| Cf. A067132.
Sequence in context: A157372 A020649 A183024 * A094915 A187186 A081147
Adjacent sequences: A067128 A067129 A067130 * A067132 A067133 A067134
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KEYWORD
| easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jan 09 2002
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EXTENSIONS
| Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Jan 15 2002
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