A126560 a(n) = gcd(4(n+1)(n+2), n(n+3)), periodic with 8-cycle 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, 4, 2, 2, 4, 8, 2, 2, 8

Offset: 1

Author

Zak Seidov, Mar 12 2007

Keywords

• nonn

Comments

a(n) = n*(3 + n)/A125650(n). Sequence is periodic with cycle 4,2,2,4,8,2,2,8.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..8192

Crossrefs

Cf. A125650.

Programs

Mathematica

Table[GCD[m(3+m),4(1+m)(2+m)],{m,48}]

PARI

A126560(n) = gcd(4*(n+1)*(n+2),n*(n+3)); \\ Antti Karttunen, Aug 11 2017

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]

Extensions

More terms from Antti Karttunen, Aug 11 2017