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A109014 a(n) = gcd(n,11). 4

%I

%S 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,

%T 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,

%U 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

%N a(n) = gcd(n,11).

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

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

%F Multiplicative with a(p^e, 11) = gcd(p^e, 11). - _David W. Wilson_, Jun 12 2005

%F Dirichlet g.f.: zeta(s)*(1+10/11^s). - _R. J. Mathar_, Apr 08 2011

%F a(n) = ((n-1) mod 2 + 1)*(10*floor(((n-1) mod 11)/10) + 1). - _Gary Detlefs_, Dec 28 2011

%Y Cf. A109004.

%K nonn,easy,mult

%O 0,1

%A _Mitch Harris_

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Last modified September 28 19:55 EDT 2021. Contains 347717 sequences. (Running on oeis4.)