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A108849
Semiprimes whose digit reversal is a nontrivial power.
1
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
OFFSET
1,1
COMMENTS
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) ...
EXAMPLE
215 is a term because 215 = 5*43 and 512 = 2^9.
MATHEMATICA
Revfn[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[30000], Revfn[#]>1&&PrimeOmega[#]==2&&ResourceFunction["PerfectPowerQ"][Revfn[#]]&] (* James C. McMahon, Apr 02 2024 *)
PROG
(PARI) isok(n) = (bigomega(n)==2) && ispower(subst(Polrev(digits(n)), x, 10)); \\ Michel Marcus, Jun 03 2016
CROSSREFS
Cf. A069798.
Sequence in context: A024053 A197970 A048892 * A375910 A025558 A298986
KEYWORD
base,nonn
AUTHOR
Jason Earls, Jul 11 2005
STATUS
approved