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Search: id:A110878
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| A110878 |
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Positive integers n such that the sum of the divisors of n, excluding 1, is a multiple of the number of divisors of n. |
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+0
1
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| 1, 2, 4, 9, 16, 25, 36, 64, 81, 100, 121, 289, 400, 529, 625, 729, 841, 1024, 1089, 1296, 1681, 2025, 2116, 2209, 2304, 2401, 2809, 3025, 3481, 4096, 5041, 6724, 6889, 7569, 7921, 10201, 11449, 12769, 13456, 13924, 15625, 17161, 18769, 19881
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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It appears that all terms except the second are squares. This has been verified for all terms less than one million.
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EXAMPLE
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The 9 divisors of 36 are {1,2,3,4,6,9,12,18,36}, giving sigma(36)-1=90 which is a multiple of 9. Thus 36 is a term of the sequence.
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CROSSREFS
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Sequence in context: A015730 A073858 A006474 this_sequence A077137 A023194 A114080
Adjacent sequences: A110875 A110876 A110877 this_sequence A110879 A110880 A110881
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Sep 19 2005
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