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A108849
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Semiprimes whose digit reversal is a nontrivial power.
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1
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4, 9, 46, 94, 121, 169, 215, 526, 961, 982, 1042, 1273, 1405, 1843, 2918, 3194, 4069, 4633, 5213, 5221, 6313, 6511, 6937, 8402, 9235, 9481, 9586, 9886, 10201, 10609, 12538, 12769, 14023, 16171, 16327, 16582, 16723, 18085, 18463, 18811, 27845
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OFFSET
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1,1
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COMMENTS
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Some nonsquare brilliant numbers in the sequence: 70597 = 227*311 (79507 = 43^3), 76121 = 163*467 (12167 = 23^3), 211591 = 457*463 (195112 = 58^3), 291149 = 359*811 (941192 = 98^3) ...
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LINKS
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EXAMPLE
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215 is a term because 215 = 5*43 and 512 = 2^9.
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MATHEMATICA
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Revfn[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[30000], Revfn[#]>1&&PrimeOmega[#]==2&&ResourceFunction["PerfectPowerQ"][Revfn[#]]&] (* James C. McMahon, Apr 02 2024 *)
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PROG
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(PARI) isok(n) = (bigomega(n)==2) && ispower(subst(Polrev(digits(n)), x, 10)); \\ Michel Marcus, Jun 03 2016
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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