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A073172
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The value of index for composite numbers with square subscripts which are also square numbers.
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1
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1, 4, 9, 1024, 5621641, 10188864, 27657081, 308950929, 619113924, 904265041, 10011203136
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OFFSET
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1,2
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LINKS
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FORMULA
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Solutions to c[x^2]=y^2, values of x^2; where c(j)=j-th composite number; See program.
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EXAMPLE
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a(4)=1024 corresponds to composite=1225=35.35=c(1024)=c(32.32).
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MATHEMATICA
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c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Do[s=c[n^2]; If[IntegerQ[Sqrt[s]], Print[n^2]], {n, 1, 1000000}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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