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A060780
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a(n) = gcd(sigma(n+1), sigma(n)) = gcd(A000203(n+1), A000203(n)).
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8
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1, 1, 1, 1, 6, 4, 1, 1, 1, 6, 4, 14, 2, 24, 1, 1, 3, 1, 2, 2, 4, 12, 12, 1, 1, 2, 8, 2, 6, 8, 1, 3, 6, 6, 1, 1, 2, 4, 2, 6, 6, 4, 4, 6, 6, 24, 4, 1, 3, 3, 2, 2, 6, 24, 24, 40, 10, 30, 12, 2, 2, 8, 1, 1, 12, 4, 2, 6, 48, 72, 3, 1, 2, 2, 4, 4, 24, 8, 2, 1, 1, 42, 28, 4, 12, 12, 60, 90, 18, 2, 56, 8
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OFFSET
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1,5
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LINKS
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MAPLE
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seq(igcd(numtheory:-sigma(n+1), numtheory:-sigma(n)), n=1..100); # Robert Israel, Jul 03 2017
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MATHEMATICA
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Table[GCD[DivisorSigma[1, n + 1], DivisorSigma[1, n]] , {n, 1, 50}] (* G. C. Greubel, Jul 03 2017 *)
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PROG
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(PARI) t=1; for (n=1, 1000, s=sigma(n+1); write("b060780.txt", n, " ", gcd(s, t)); t=s) \\ Harry J. Smith, Jul 11 2009
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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