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Search: id:A115646
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| A115646 |
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Semiprimes (A001358) that are sums of distinct factorials. |
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+0
3
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| 6, 9, 25, 26, 33, 121, 122, 123, 129, 145, 146, 721, 723, 745, 746, 753, 841, 842, 843, 849, 865, 866, 871, 5041, 5042, 5065, 5071, 5161, 5163, 5169, 5186, 5191, 5761, 5767, 5793, 5905, 5906, 5911, 40321, 40322, 40323, 40345, 40346, 40353, 40441
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Factorials 0! and 1! are not considered distinct.
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EXAMPLE
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721 = 6!+1! = 7*103.
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MATHEMATICA
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semipQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2; fac=Range[10]!; lst={}; Do[ n = Plus@@(fac*IntegerDigits[k, 2, 10]); If[semipQ[n], AppendTo[lst, n]], {k, 2^10-1}]; Union[lst]
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CROSSREFS
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Cf. A001358, A025494, A115645, A115644, A089359.
Sequence in context: A084431 A142877 A093153 this_sequence A115644 A024878 A007414
Adjacent sequences: A115643 A115644 A115645 this_sequence A115647 A115648 A115649
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KEYWORD
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nonn
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AUTHOR
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Giovanni Resta (g.resta(AT)iit.cnr.it), Jan 27 2006
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