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A126560
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GCD[4(n+1)(n+2),n(n+3)].
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0
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = n*(3 + n)/A125650(n). Sequence is periodic with cycle 4,2,2,4,8,2,2,8.
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FORMULA
| a(n) = GCD[4(n+1)(n+2),n(n+3)]
a(n)=(1/28)*{18*[n mod 8]-17*[(n+1) mod 8]+4*[(n+2) mod 8]+25*[(n+3) mod 8]-10*[(n+4) mod 8]-3*[(n+5) mod 8]+4*[(n+6) mod 8]+11*[(n+7) mod 8]}, with n>=0. - Paolo P. Lava (paoloplava(AT)gmail.com), Jun 01 2007
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 (richardchoulet(AT)yahoo.fr), Dec 11 2008]
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MATHEMATICA
| Table[GCD[m(3+m), 4(1+m)(2+m)], {m, 48}]
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CROSSREFS
| Cf. A125650.
Sequence in context: A100854 A194688 A021707 * A064213 A016510 A023634
Adjacent sequences: A126557 A126558 A126559 * A126561 A126562 A126563
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Mar 12 2007
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