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A089129
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Greatest common divisor of n^2-7 and n^2+7.
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1
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7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1, 2, 1, 2, 1, 14, 1, 2, 1, 2, 1, 2, 7, 2, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| a(n) is the product of the periodic sequences [1,2]*[7,1,1,1,1,1,1].
[From Gary Detlefs (gdetlefs(AT)aol.com), Apr 22 2011]
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..1000
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FORMULA
| Contribution from Gary Detlefs (gdetlefs(AT)aol.com), Apr 22 2011: (Start)
a(n)=gcd(n+7,14)
a(n)=(6*(1-(n^6 mod 7))+1)*((n mod 2)+1). (End)
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PROG
| (PARI) g(n, k) = for(x=0, n, print1(gcd(x^k-7, x^k+7)", "))
(MAGMA) [Gcd(n^2+7, n^2-7): n in [0..100] ]; // Vincenzo Librandi, Apr 22 2011
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CROSSREFS
| Sequence in context: A021585 A103713 A197184 * A100957 A191856 A198229
Adjacent sequences: A089126 A089127 A089128 * A089130 A089131 A089132
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Dec 05 2003
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