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%I #16 Sep 08 2022 08:45:09
%S 0,1,2,3,4,5,6,7,8,9,7,8,9,10,11,12,13,14,15,16,14,15,16,17,18,19,20,
%T 21,22,23,21,22,23,24,25,26,27,28,29,30,28,29,30,31,32,33,34,35,36,37,
%U 35,36,37,38,39,40,41,42,43,44,42,43,44,45,46,47,48,49,50,51,49,50,51,52,53,54
%N Let n = 10x + y where 0 <= y <= 9, x >= 0. Then a(n) = 7x+y.
%H Vincenzo Librandi, <a href="/A081598/b081598.txt">Table of n, a(n) for n = 0..2000</a>
%F G.f.: -x*(2*x^9 -x^8 -x^7 -x^6 -x^5 -x^4 -x^3 -x^2 -x -1) / ((x -1)^2*(x +1)*(x^4 -x^3 +x^2 -x +1)*(x^4 +x^3 +x^2 +x +1)). - _Colin Barker_, Jun 24 2014
%F a(n) = n - 3*floor(n/10). [_Bruno Berselli_, Jun 24 2014]
%t CoefficientList[Series[-x (2 x^9 - x^8 - x^7 - x^6 - x^5 - x^4 - x^3 - x^2 - x - 1)/((x - 1)^2 (x + 1) (x^4 - x^3 + x^2 - x + 1) (x^4 + x^3 + x^2 + x + 1)), {x, 0, 150}], x] (* _Vincenzo Librandi_, Jun 25 2014 *)
%t Table[n-3*Floor[n/10],{n,0,80}] (* _Harvey P. Dale_, Apr 22 2019 *)
%o (PARI) my(n, x, y); vector(200, n, y=(n-1)%10; x=(n-1-y)\10; 7*x+y) \\ _Colin Barker_, Jun 24 2014
%o (Magma) k:=7; [n-(10-k)*Floor(n/10): n in [0..100]]; // _Bruno Berselli_, Jun 24 2014
%Y Cf. A081502. Different from A028902.
%K nonn
%O 0,3
%A _N. J. A. Sloane_, Apr 22 2003
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