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A283670
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The single square referenced in A190641.
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2
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4, 4, 9, 4, 4, 9, 4, 4, 25, 9, 4, 4, 4, 4, 9, 4, 49, 25, 4, 9, 4, 4, 9, 4, 4, 25, 4, 4, 9, 4, 4, 9, 4, 4, 49, 9, 4, 4, 4, 9, 4, 121, 4, 25, 9, 4, 4, 9, 4, 4, 49, 4, 25, 4, 9, 4, 4, 9, 4, 4, 169, 9, 4, 25, 4, 4, 4, 9, 4, 9, 4, 9, 4, 4, 4, 4, 4, 4, 9, 4, 4
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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A190641(4) = 12, 12 = 2*2*3, so 12 has only one square factor, namely 4.
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MATHEMATICA
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f[n_] := Module[{f = FactorInteger[n], ind}, ind = Position[f[[;; , 2]], _?(# > 1 &)]; If[Length[ind] == 1, f[[ind[[1, 1]], 1]]^2, Nothing]]; Array[f, 300] (* Amiram Eldar, Jul 28 2024 *)
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PROG
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(PARI) lista(kmax) = for(k = 1, kmax, my(f = factor(k)); if(#select(x -> (x>1), f[, 2]) == 1, for(i = 1, #f~, if(f[i, 2] > 1, print1(f[i, 1]^2, ", "); break)))); \\ Amiram Eldar, Jul 28 2024
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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