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A066025
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Numbers n such that GCD(Sigma(n), Sigma(n+1)) > n.
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1
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5, 12, 14, 70, 88, 125, 180, 204, 206, 220, 957, 1253, 1334, 1364, 1634, 1673, 1750, 1888, 1919, 2685, 2759, 2958, 2974, 3127, 4364, 5191, 7615, 8142, 8632, 9114, 11219, 12000, 12035, 14664, 14841, 18414, 18762, 18873, 19358, 20118
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
| GCD(Sigma(12), Sigma(13)) = GCD(28, 14) = 14 > 12.
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MATHEMATICA
| Select[Range[1, 10^5], GCD[DivisorSigma[1, # ], DivisorSigma[ 1, # + 1]] > # &]
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PROG
| (PARI) { n=0; s=1; for (m=1, 10^9, t=s; s=sigma(m + 1); if (gcd(t, s) > m, write("b066025.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Nov 07 2009]
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CROSSREFS
| Cf. A000010.
Sequence in context: A114073 A185871 A037007 * A009824 A087090 A161756
Adjacent sequences: A066022 A066023 A066024 * A066026 A066027 A066028
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 11 2001
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EXTENSIONS
| Definition and EXAMPLE edited by Harry J. Smith (hjsmithh(AT)sbcglobal.net), Nov 07 2009
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