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A054903
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Composite numbers n such that sigma(n)+6 = sigma(n+6), where sigma=A000203.
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4
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104, 147, 596, 1415, 4850, 5337, 370047, 1630622, 35020303, 120221396, 3954451796, 742514284703
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OFFSET
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1,1
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COMMENTS
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Below 1000000 there are only 7 such composite numbers, compared with more than 16000 primes.
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REFERENCES
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J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 104, p. 37, Ellipses, Paris 2008.
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LINKS
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EXAMPLE
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n=104, sigma(104)+6 = 210+6 = 216 = sigma(104+6) = sigma(110).
a(4) = 1415 = 5*283, 1415+6 = 1421 = 7*7*29:
sigma(1415) = 1+5+283+1415 = 1704,
sigma(1421) = 1+7+29+49+203+1421 = 1710 = sigma(1415)+6.
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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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