A109045 a(n) = lcm(n,4).

0, 4, 4, 12, 4, 20, 12, 28, 8, 36, 20, 44, 12, 52, 28, 60, 16, 68, 36, 76, 20, 84, 44, 92, 24, 100, 52, 108, 28, 116, 60, 124, 32, 132, 68, 140, 36, 148, 76, 156, 40, 164, 84, 172, 44, 180, 92, 188, 48, 196, 100, 204, 52, 212, 108, 220, 56, 228, 116, 236, 60

Offset: 0

Author

Mitch Harris, Jun 18 2005

Keywords

• nonn
• easy

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
• Index entries for linear recurrences with constant coefficients, signature (0,0,0,2,0,0,0,-1).
• Index entries for sequences related to lcm's.

Crossrefs

Cf. A060819, A084351, A109008, A109042.

Programs

Haskell

a109045 = lcm 4  -- Reinhard Zumkeller, Nov 25 2013

Magma

[Lcm(n,4): n in [0..100]]; // Vincenzo Librandi, Apr 18 2011

Mathematica

Table[LCM[n,4],{n,0,80}] (* Harvey P. Dale, May 02 2011 *)

PARI

a(n) = lcm(n, 4); \\ Michel Marcus, Mar 07 2018

Formula

a(n) = 4n/gcd(n, 4).

a(n) = A084351(n), n > 1. - R. J. Mathar, Aug 20 2008

From R. J. Mathar, Apr 18 2011: (Start)

G.f.: 4*x*(1+x+3*x^2+x^3+3*x^4+x^5+x^6) / ( (x-1)^2*(1+x)^2*(x^2+1)^2 ).

a(n) = 4*n/A109008(n) = 4*A060819(n). (End)

Sum_{k=1..n} a(k) ~ (11/8) * n^2. - Amiram Eldar, Nov 26 2022