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Search: id:A075768
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| A075768 |
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A Wallis pair (x,y) satisfies sigma(x^2) = sigma(y^2); sequence gives x's for indecomposable Wallis pairs with x < y (ordered by values of x). |
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5
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| 4, 326, 406, 627, 740, 880, 888, 1026, 1110, 1284, 1510, 1528, 2013, 2072, 3216, 3260, 3912, 4866, 4946, 5064, 5064, 5829, 7248, 9768, 10536, 10686, 11836, 12122, 13066, 13398, 13986, 14248, 14397, 15000, 15000, 15430, 15504, 15544, 15544
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OFFSET
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0,1
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COMMENT
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If (x,y) and (u,v) are Wallis pairs, a is from (x,y) and c is from (u,v) and gcd(a,c)=1, b is from (x,y) and d is from(u,v) and gcd(b,d)=1, then (ac,bd) is also a Wallis pair. Such pairs are called decomposable. If (x,y) and (cx,cy) are Wallis pairs then (cx,cy) is also called decomposable.
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REFERENCES
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I. Kaplansky, The challenges of Fermat, Wallis and Ozanam (and several related challenges): II. Fermat's second challenge, Preprint, 2002.
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EXAMPLE
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(4,5) is a Wallis pair since sigma(16) = sigma(25) = 31.
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CROSSREFS
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Cf. A075769, A072182, A072186, A077053.
Sequence in context: A034226 A053917 A005832 this_sequence A135442 A086895 A090086
Adjacent sequences: A075765 A075766 A075767 this_sequence A075769 A075770 A075771
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KEYWORD
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nonn,nice
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AUTHOR
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njas, Oct 13 2002
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EXTENSIONS
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Corrected and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Oct 22 2002
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