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

1,1

Comments

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

Index entries for linear recurrences with constant coefficients, signature (1,-1,1,-1,1,-1,1).

Formula

a(n) = n*(3 + n)/A125650(n).

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). - 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

Adjacent sequences: A126557 A126558 A126559 * A126561 A126562 A126563

Keyword

nonn,easy

Author

Zak Seidov, Mar 12 2007

Extensions

More terms from Antti Karttunen, Aug 11 2017

Status

approved