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Search: id:A063715
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| A063715 |
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Number of solutions (r,u,s,t) in positive integers to the system of equations 1/r+1/u=1/n, 1/s+1/t=1/u. |
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+0
2
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| 3, 17, 29, 49, 45, 111, 37, 115, 109, 159, 69, 319, 45, 207, 279, 191, 69, 367, 69, 487, 315, 183, 93, 681, 141, 235, 291, 495, 117, 909, 53, 357, 331, 259, 559, 967, 45, 279, 459, 949, 117, 1025, 69, 663, 815, 219, 117, 1205, 161, 591, 411, 555, 93, 965, 579
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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a(n) = Sum_{d|n^2} tau((n+d)^2).
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EXAMPLE
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For n=2 we have 17 solutions (r,u,s,t): (3,6,7,42), (3,6,8,24), (3,6,9,18), (3,6,10,15), (3,6,12,12), (3,6,15,10), (3,6,18,9), (3,6,24,8), (3,6,42,7), (4,4,5,20), (4,4,6,12), (4,4,8,8), (4,4,12,6), (4,4,20,5), (6,3,4,12), (6,3,6,6), (6,3,12,4).
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CROSSREFS
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Cf. A000005, A048691, A063716, A048691, A004194, A063520.
Sequence in context: A106085 A007490 A022887 this_sequence A105411 A107158 A152529
Adjacent sequences: A063712 A063713 A063714 this_sequence A063716 A063717 A063718
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 10 2001
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