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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| 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
| a(4)=1024 corresponds to composite=1225=35.35=c(1024)=c(32.32).
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MATHEMATICA
| 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
| Cf. A002808, A073171.
Sequence in context: A027522 A028869 A179935 * A168139 A111443 A051499
Adjacent sequences: A073169 A073170 A073171 * A073173 A073174 A073175
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Jul 19 2002
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EXTENSIONS
| a(9)-a(11) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 24 2011
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