A109014 a(n) = gcd(n,11).

11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

Offset: 0

Author

Mitch Harris

Keywords

• nonn
• easy
• mult

Crossrefs

Cf. A109004.

Programs

Mathematica

GCD[Range[0,100],11] (* Harvey P. Dale, May 14 2022 *)

Python

from math import gcd
def a(n): return gcd(n, 11)
print([a(n) for n in range(99)]) # Michael S. Branicky, Nov 01 2021

Formula

a(n) = 1 + 10*[11|n], where [x|y] = 1 when x divides y, 0 otherwise.

a(n) = a(n-11).

Multiplicative with a(p^e, 11) = gcd(p^e, 11). - David W. Wilson, Jun 12 2005

Dirichlet g.f.: zeta(s)*(1+10/11^s). - R. J. Mathar, Apr 08 2011

a(n) = ((n-1) mod 2 + 1)*(10*floor(((n-1) mod 11)/10) + 1). - Gary Detlefs, Dec 28 2011