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A166850
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Numbers n such that reversal(n!-n) is prime.
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0
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OFFSET
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1,1
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COMMENTS
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It's obvious that there is no number n such that n!-n is prime.
There is no further term up to 5000.
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LINKS
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EXAMPLE
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56!-56=
710998587804863451854045647463724949736497978881168458687447039999999999944
and reversal(56!-56)=
449999999999930744786854861188879794637949427364746540458154368408785899017
is prime so 56 is in the sequence.
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MATHEMATICA
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reversal[n_]:=FromDigits[Reverse[IntegerDigits[n]]];
Do[If[PrimeQ[reversal[n!-n]], Print[n]], {n, 5000}]
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CROSSREFS
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KEYWORD
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base,hard,more,nonn
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AUTHOR
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STATUS
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approved
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