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Search: id:A054799
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| A054799 |
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Integers n such that Sigma[n+2]=Sigma[n]+2, Sigma=A000203, sum of divisors of n. |
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17
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| 3, 5, 11, 17, 29, 41, 59, 71, 101, 107, 137, 149, 179, 191, 197, 227, 239, 269, 281, 311, 347, 419, 431, 434, 461, 521, 569, 599, 617, 641, 659, 809, 821, 827, 857, 881, 1019, 1031, 1049, 1061, 1091, 1151, 1229, 1277, 1289, 1301, 1319, 1427, 1451, 1481, 1487
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OFFSET
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1,1
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COMMENT
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Below 1000000 only 3 composite numbers were found: 434, 8575, 8825. This sequence is different from A001359.
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REFERENCES
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Sivaramakrishnan, R. (1989): Classical Theory of Arithmetical Functions., M.Dekker Inc., New York, Problem 12 in Chapter V., p. 81.
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EXAMPLE
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n = 434, divisors = {1, 2, 7, 14, 31, 62, 217, 434}, Sigma[434] = 768, Sigma[436] = 770; n = 8575, divisors = {1, 5, 7, 25, 35, 49, 175, 245, 343, 1225, 1715, 8575}, Sigma[8575] = 12400, Sigma[8577] = 12402; n = 8825, divisors = {1, 5, 25, 353, 1765, 8825}, Sigma[8525] = 10974, Sigma[8527] = 10976
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CROSSREFS
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Cf. A000203, A001359, A050507.
Adjacent sequences: A054796 A054797 A054798 this_sequence A054800 A054801 A054802
Sequence in context: A069233 A063700 A078859 this_sequence A001359 A096292 A078864
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 22 2000
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