This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A180596 #19 Jun 11 2022 14:08:47
%S A180596 0,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,
%T A180596 6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,
%U A180596 3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3,9,6,3
%N A180596 Digital root of 6n.
%C A180596 Period of 3. - _Robert G. Wilson v_, Sep 20 2010
%H A180596 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1).
%F A180596 G.f.: 3*x*(2 + x + 3*x^2)/(1 - x^3). - _Stefano Spezia_, Apr 21 2022
%F A180596 a(n) = A010888(A008588(n)). - _Michel Marcus_, Apr 24 2022
%t A180596 f[n_] := Mod[6 n - 1, 9] + 1; f[0] = 0; Array[f, 105, 0] (* _Robert G. Wilson v_, Sep 20 2010 *)
%t A180596 PadRight[{0},120,{9,6,3}] (* _Harvey P. Dale_, Dec 18 2012 *)
%Y A180596 Cf. A010888, A008588.
%Y A180596 Cf. A180592, A180593, A180594, A180595, A180597, A180598, A180599.
%Y A180596 Column k = 6 in A353109.
%K A180596 easy,nonn,base
%O A180596 0,2
%A A180596 _Odimar Fabeny_, Sep 10 2010
%E A180596 More terms from _Robert G. Wilson v_, Sep 20 2010