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Search: id:A072394
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| A072394 |
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Numbers n such that sigma(n)=reversal(n)-n. |
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1
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| 1563, 1633, 18673, 32207, 1405313, 1567563, 1656833, 193613415, 325933027, 376491249, 2287850446, 2432416646, 13823276223, 14055445313, 19087920283, 23804849568, 36303512827
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OFFSET
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1,1
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COMMENT
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If (58*1000^n-169)/111 is prime then (58*1000^n-169)/37 is in the sequence (the proof is easy). Next term is greater than 12*10^8. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Jan 29 2006
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EXAMPLE
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reverse(1563) - 1563 = 3651 - 1563 = 2088 = sigma(1563), so 1563 is a term of the sequence.
376491249 is in the sequence because sigma(376491249)=565703424 =942194673-376491249=reversal(376491249)-376491249.
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MATHEMATICA
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Select[Range[10^6], FromDigits[Reverse[IntegerDigits[n]]] - # == DivisorSigma[1, # ] &]
Do[If[DivisorSigma[1, n]==FromDigits[Reverse[IntegerDigits[n]]]- n, Print[n]], {n, 1200000000}] (Firoozbakht)
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CROSSREFS
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Cf. A072234.
Sequence in context: A158773 A035865 A031800 this_sequence A035890 A045276 A099542
Adjacent sequences: A072391 A072392 A072393 this_sequence A072395 A072396 A072397
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe (JosephL.Pe(AT)hotmail.com), Jul 21 2002
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EXTENSIONS
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More terms from Farideh Firoozbakht (mymontain(AT)yahoo.com), Jan 29 2006
a(11)-a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 21 2008
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