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A126560
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a(n) = gcd(4(n+1)(n+2), n(n+3)), periodic with 8-cycle 4,2,2,4,8,2,2,8.
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1
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4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8, 4, 2, 2, 4, 8, 2, 2, 8
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OFFSET
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1,1
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COMMENTS
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a(n) = n*(3 + n)/A125650(n). Sequence is periodic with cycle 4,2,2,4,8,2,2,8.
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LINKS
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FORMULA
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a(n) = GCD[4(n+1)(n+2),n(n+3)]
a(n)=4+(-1+1/2*2^(1/2))*cos(Pi*n/4)-1/2*2^(1/2)*sin(Pi*n/4)+(-1/2*2^(1/2)-1)*cos(3*Pi*n/4)-1/2*2^(1/2)*sin(3*Pi*n/4)+2*cos(n*Pi/2)-2*sin(n*Pi/2) [From Richard Choulet, Dec 11 2008]
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MATHEMATICA
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Table[GCD[m(3+m), 4(1+m)(2+m)], {m, 48}]
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PROG
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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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