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Search: id:A071375
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| A071375 |
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Smallest m such that number of square-free divisors of m equals n; a(n)=0 if no solution to A048250[x]=n exists. |
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1
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| 1, 0, 2, 3, 0, 5, 0, 7, 0, 0, 0, 6, 0, 13, 0, 0, 0, 10, 0, 19, 0, 0, 0, 14, 0, 0, 0, 0, 0, 29, 0, 21, 0, 0, 0, 22, 0, 37, 0, 0, 0, 26, 0, 43, 0, 0, 0, 33, 0, 0, 0, 0, 0, 34, 0, 39, 0, 0, 0, 38, 0, 61, 0, 0, 0, 0, 0, 67, 0, 0, 0, 30, 0, 73, 0, 0, 0, 0, 0, 57, 0, 0, 0, 65, 0, 0, 0, 0, 0, 58, 0, 0, 0, 0
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OFFSET
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1,3
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FORMULA
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a(n)=Min{x; A048250[x]=n}, a(n)=0 if no solutions.
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EXAMPLE
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n=256: a(256)=217=7.31, all divisors are square-free and 1+7+31+217=256=n.
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MATHEMATICA
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ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] cor[x_] := Apply[Times, ba[x]] t=Table[0, {256}]; Do[s=DivisorSigma[1, cor[n]]; If[s<257&&t[[s]]==0, t[[s]]=n], {n, 1, 1000000}]; t
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CROSSREFS
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Cf. A048250.
Sequence in context: A126436 A102394 A085563 this_sequence A061397 A093438 A047814
Adjacent sequences: A071372 A071373 A071374 this_sequence A071376 A071377 A071378
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 22 2002
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