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A281265
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Variation on betrothed numbers.
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0
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6160, 11697, 12220, 16005, 23500, 28917, 68908, 76245, 249424, 339825, 425500, 434784, 570405, 649990, 660825, 678376, 697851, 871585, 1017856, 1077336, 1238380, 1252216, 1340865, 1483785, 1568260, 1754536, 1823925, 1899261, 2067625, 2166136, 2362360, 2479065
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OFFSET
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1,1
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COMMENTS
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Members of a pair (x,y) such that sigma(x) = sigma(y) = x + y - 1, where sigma = A000203.
The first time a pair ordered by its first element is not adjacent is x = 425500, y = 570405 which correspond to a(11) and a(13), respectively.
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LINKS
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FORMULA
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EXAMPLE
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sigma(6160) = sigma(11697) = 6160 + 11697 - 1 = 17856.
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MAPLE
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with(numtheory): P:=proc(q) local a, b, n; for n from 1 to q do
a:=sigma(n)-n+1; b:=sigma(a)-a+1; if b=n and a<>b then print(n);
fi; od; end: P(10^9);
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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