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A115707
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Pentagonal numbers (A000326) whose digit reversal is a prime.
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2
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5, 35, 70, 92, 145, 376, 1520, 1820, 3577, 3725, 7526, 9322, 9560, 10045, 10292, 13490, 14065, 16801, 17767, 18760, 32782, 34126, 34580, 36895, 38320, 38801, 39772, 73151, 74482, 76501, 78547, 91390, 93625, 94376, 98176, 100492, 101270
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OFFSET
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1,1
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LINKS
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EXAMPLE
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145 is the 10th pentagonal number and 541 is prime.
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MATHEMATICA
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Select[Table[n (3n-1)/2, {n, 400}], PrimeQ[FromDigits[Reverse[ IntegerDigits[ #]]]]&] (* Harvey P. Dale, Feb 23 2011 *)
Select[PolygonalNumber[5, Range[300]], PrimeQ[IntegerReverse[#]]&] (* Harvey P. Dale, Mar 27 2024 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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