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%I #35 Dec 12 2023 08:52:00
%S 1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,
%T 4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,
%U 2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2,7,4,2,1,1,2,4,7,2
%N Period 9: repeat [1, 1, 2, 4, 7, 2, 7, 4, 2].
%C For n>0, digital roots of centered 10-gonal numbers (A062786). - _Colin Barker_, Jan 30 2015
%C For n>0, also the digital roots of central polygonal numbers (the Lazy Caterer's sequence) A000124. - _Peter M. Chema_, Sep 17 2016
%H Colin Barker, <a href="/A133292/b133292.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,1).
%F G.f.: -(2*x^8+4*x^7+7*x^6+2*x^5+7*x^4+4*x^3+2*x^2+x+1) / ((x-1)*(x^2+x+1)*(x^6+x^3+1)). - _Colin Barker_, Apr 04 2015
%F a(n) = a(n-9). - _Wesley Ivan Hurt_, May 09 2022
%t PadRight[{},111,{1,1,2,4,7,2,7,4,2}] (* _Harvey P. Dale_, Apr 29 2012 *)
%o (PARI) a(n)=[1,1,2,4,7,2,7,4,2][n%9+1] \\ _Charles R Greathouse IV_, Jun 02 2011
%o (PARI) Vec(-(2*x^8+4*x^7+7*x^6+2*x^5+7*x^4+4*x^3+2*x^2+x+1)/((x-1)*(x^2+x+1)*(x^6+x^3+1)) + O(x^100)) \\ _Colin Barker_, Apr 04 2015
%Y Cf. A000124, A062786.
%K nonn,easy,less
%O 0,3
%A _Paul Curtz_, Oct 17 2007
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