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Search: id:A115354
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| A115354 |
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a(n) is the smallest number representable in exactly n ways as a sum of 2 powerful(1) numbers. |
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+0
2
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| 2, 17, 108, 153, 297, 657, 1764, 2052, 4644, 6156, 10800, 16200, 22932, 29000, 11025, 54225, 92025, 68796, 100548, 99225, 44100, 88200
(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 = 16+1 = 8+9.
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MATHEMATICA
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pwfQ[n_] := n == 1 || Min[Transpose[FactorInteger@n][[2]]] > 1; lim=200000; pt = Select[Range[lim], pwfQ]; t = Table[0, {i, lim}]; Do[v = pt[[i]]+ pt[[j]]; If[v<=lim, t[[v]]++ ], {i, Length@pt}, {j, i}]; Table[Position[t, k][[1, 1]], {k, 22}]
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CROSSREFS
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Cf. A001694, A085252, A085253, A085254, A085255, A063274, A115355.
Adjacent sequences: A115351 A115352 A115353 this_sequence A115355 A115356 A115357
Sequence in context: A119363 A129977 A105652 this_sequence A100274 A037747 A037628
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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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