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A126560
a(n) = gcd(4(n+1)(n+2), n(n+3)), periodic with 8-cycle 4,2,2,4,8,2,2,8.
1
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
OFFSET
1,1
COMMENTS
a(n) = n*(3 + n)/A125650(n). Sequence is periodic with cycle 4,2,2,4,8,2,2,8.
LINKS
FORMULA
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]
MATHEMATICA
Table[GCD[m(3+m), 4(1+m)(2+m)], {m, 48}]
PROG
(PARI) A126560(n) = gcd(4*(n+1)*(n+2), n*(n+3)); \\ Antti Karttunen, Aug 11 2017
CROSSREFS
Cf. A125650.
Sequence in context: A317389 A322510 A021707 * A289762 A360855 A064213
KEYWORD
nonn
AUTHOR
Zak Seidov, Mar 12 2007
EXTENSIONS
More terms from Antti Karttunen, Aug 11 2017
STATUS
approved