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A181647
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Numbers m having the same sum of divisors as m+20 has.
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15
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42, 51, 123, 141, 204, 371, 497, 708, 923, 992, 1034, 1343, 1391, 1484, 1595, 1691, 1826, 3266, 3317, 5015, 5152, 7367, 8003, 9132, 9287, 9494, 11078, 13223, 15458, 15833, 17975, 18752, 19428, 20120, 20915, 21251, 21566, 24119, 24503, 25787
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OFFSET
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1,1
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COMMENTS
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REFERENCES
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J.-M. De Koninck, Those Fascinating Numbers, Amer. Math. Soc., 2009, page 16.
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LINKS
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EXAMPLE
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a(1)=42, divisors(42)={1,2,3,6,7,14,21,42}, divisors(42+20)={1,2,31,62}: 1+2+3+6+7+14+21+42=1+2+31+62.
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PROG
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(PARI) isok(n) = sigma(n) == sigma(n+20); \\ Michel Marcus, Feb 06 2016
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CROSSREFS
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Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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