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A215478
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Semiprimes with digits in descending order that differ exactly by 1.
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1
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4, 6, 9, 10, 21, 65, 87, 321, 543, 4321, 8765, 98765, 654321, 876543, 7654321
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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4321 is in the sequence because it is semiprime 4321 = 29 * 149, and (4,3,2,1) are descending consecutive digits.
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MATHEMATICA
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Sort[Flatten[Table[Select[FromDigits/@Partition[Range[9, 0, -1], n, 1], PrimeOmega[#] == 2&], {n, 10}]]] (* Harvey P. Dale, Jul 10 2014 *)
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CROSSREFS
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KEYWORD
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nonn,base,easy,full,fini
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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