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Search: id:A066531
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| A066531 |
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EPRNs (Equal Product Of Reversible Numbers): numbers which can be expressed as the product of two reversible numbers in two different ways. |
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+0
10
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| 2520, 4030, 5740, 7360, 7650, 9760, 10080, 12070, 13000, 14580, 14620, 16120, 17290, 18550, 19440, 22680, 22960, 24300, 25200, 26680, 27010, 29440, 31540, 34780, 36270, 36400, 40300, 40320, 42750, 46060, 49300, 50920, 56050, 57400
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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All EPRNs are even numbers. The digital root i.e. ultimate sum of digits of all EPRNs is always 1,4,7 or 9.
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REFERENCES
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S. S. Gupta, EPRNs, Science Today, Feb. 1987, India.
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LINKS
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Shyam Sunder Gupta, EPRN Numbers
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EXAMPLE
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4030 = 130 * 031 = 310 * 013, 144648 = 861 * 168 = 492 * 294, 185472 = 672 * 276 = 384 * 483, 9949716 = 2583 * 3852 = 1476 * 6741, 16746912 = 2556 * 6552 = 4473 * 3744, etc.
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MATHEMATICA
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f[n_] := (m = ToExpression[StringReverse[ToString[n]]]; If[n > m, n*m, 0]); a = Sort[ Table[ f[n], {n, 0, 10^4}]]; While[ a[[1]] == 0, a = Drop[a, 1]]; a[[ Select[ Range[ Length[a]] - 1, a[[ # ]] == a[[ # + 1 ]] & ]]]
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CROSSREFS
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Sequence in context: A068352 A068547 A094515 this_sequence A159214 A064592 A109480
Adjacent sequences: A066528 A066529 A066530 this_sequence A066532 A066533 A066534
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 06 2002
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