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Search: id:A115355
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| A115355 |
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a(n) is the smallest number representable in exactly n ways as a sum of 3 powerful(1) numbers. |
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+0
2
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| 3, 17, 33, 41, 66, 77, 89, 117, 133, 145, 153, 189, 161, 225, 301, 257, 324, 333, 341, 297, 432, 425, 369, 517, 613, 441, 521, 585, 513, 809, 689, 792, 657, 1001, 801, 881, 1000, 1017, 873, 945, 900, 1265, 1169, 1425, 1089, 1125, 1197, 1481, 1161, 1584
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Here we are considering powerful numbers (first definition) A001694. Note that, by definition, 1 is powerful.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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EXAMPLE
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a(2)=17 since 17 = 4+4+9 =8+8+1.
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MATHEMATICA
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pwfQ[n_] := n==1 || Min[Transpose[FactorInteger@n][[2]]] > 1; lim = 5000; pt = Select[Range[lim], pwfQ]; t = Table[0, {i, lim}]; Do[v = pt[[i]]+pt[[j]]+pt[[k]]; If[v <= lim, t[[v]]++ ], {i, Length@pt}, {j, i}, {k, j}]; Table[Position[t, k][[1, 1]], {k, 60}]
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CROSSREFS
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Cf. A001694, A085252, A085253, A085254, A085255, A063274, A115354.
Sequence in context: A090648 A031024 A045437 this_sequence A031290 A031386 A106895
Adjacent sequences: A115352 A115353 A115354 this_sequence A115356 A115357 A115358
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KEYWORD
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nonn
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AUTHOR
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Giovanni Resta (g.resta(AT)iit.cnr.it), Jan 21 2006
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