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A072186
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A Wallis pair (x,y) satisfies sigma(x^2) = sigma(y^2); sequence gives y's for Wallis pairs with x < y (ordered by values of x).
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4
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5, 15, 35, 45, 55, 65, 85, 95, 105, 115, 135, 145, 155, 165, 185, 195, 205, 215, 235, 245, 255, 265, 285, 295, 305, 315, 335, 345, 355, 365, 385, 395, 405, 407, 415, 435, 445, 455, 465, 485, 495, 505, 489, 515, 535, 545, 555, 565, 585, 595, 605, 615, 635
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 5*A045572 is included in this sequence - Benoit Cloitre, Oct 22 2002
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REFERENCES
| 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
| The first few pairs are all multiples of the first pair (4,5): (4, 5), (12, 15), (28, 35), (36, 45), (44, 55), (52, 65), ...
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PROG
| (PARI) {w=[]; m=550; for(x=1, m, q=sigma(x^2); sq=sqrtint(q); for(y=x+1, sq, if(q==sigma(y^2), w=concat(w, [[x, y]])))); for(j=1, matsize(w)[2], print1(w[j][2], ", "))}
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CROSSREFS
| Cf. A072182, A075768, A075769.
Sequence in context: A083049 A015627 A156778 * A051807 A034052 A061829
Adjacent sequences: A072183 A072184 A072185 * A072187 A072188 A072189
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Oct 19 2002
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EXTENSIONS
| Extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 22 2002
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