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 A168183 #53 May 11 2025 01:12:40
%S A168183 1,2,3,4,5,6,7,8,10,11,12,13,14,15,16,17,19,20,21,22,23,24,25,26,28,
%T A168183 29,30,31,32,33,34,35,37,38,39,40,41,42,43,44,46,47,48,49,50,51,52,53,
%U A168183 55,56,57,58,59,60,61,62,64,65,66,67,68,69,70,71,73,74,75,76,77,78,79,80
%N A168183 Numbers that are not multiples of 9.
%C A168183 It seems that, for any n >= 1, there exists no positive integer z such that digit_sum(z) = digit_sum(a(n)+z). - _Max Lacoma_, Sep 19 2019. _Giovanni Resta_: this follows immediately from the well-known fact that sod(x) == x (mod 9).
%H A168183 Ivan Panchenko, <a href="/A168183/b168183.txt">Table of n, a(n) for n = 1..200</a>
%H A168183 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,0,1,-1).
%F A168183 A168182(a(n)) = 1.
%F A168183 A010888(a(n)) = A010887(n-1).
%F A168183 A109012(a(n)) < 9.
%F A168183 From _Wesley Ivan Hurt_, Sep 12 2015: (Start)
%F A168183 a(n) = a(n-1) + a(n-8) - a(n-9), n>9.
%F A168183 a(n) = n + floor((n-1)/8). (End)
%F A168183 From _Philippe Deléham_, Dec 05 2016: (Start)
%F A168183 a(n) = 1 + A248375(n-1).
%F A168183 G.f.: x*(1-x^9)/((1-x)^2*(1-x^8)). (End)
%F A168183 E.g.f.: 1 + (1/8)*(-cos(x) + (-5+9*x)*cosh(x) - 2*cos(x/sqrt(2))*cosh(x/sqrt(2)) + sin(x) + (-4+9*x)*sinh(x) + 2*sin(x/sqrt(2))*(sqrt(2)*cosh(x/sqrt(2)) + sinh(x/sqrt(2)))). - _Stefano Spezia_, Sep 20 2019
%F A168183 Sum_{n>=1} (-1)^(n+1)/a(n) = (sqrt(3) + 3*cosec(2*Pi/9) - 3*tan(Pi/18)) * Pi/27. - _Amiram Eldar_, May 11 2025
%p A168183 A168183:=n->n+floor((n-1)/8): seq(A168183(n), n=1..100); # _Wesley Ivan Hurt_, Sep 12 2015
%t A168183 Select[Table[n,{n,200}],Mod[#,9]!=0&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 18 2011 *)
%t A168183 With[{nn=81},Complement[Range[nn],9Range[Floor[nn/9]]]] (* _Harvey P. Dale_, Sep 07 2011 *)
%o A168183 (Haskell)
%o A168183 a168183 n = a168183_list !! (n-1)
%o A168183 a168183_list = [1..8] ++ map (+ 9) a168183_list
%o A168183 -- _Reinhard Zumkeller_, Mar 04 2014
%o A168183 (PARI) is(n)=!!(n%9) \\ _Charles R Greathouse IV_, Sep 02 2015
%o A168183 (PARI) a(n)=(9*n-1)\8 \\ _Charles R Greathouse IV_, Sep 02 2015
%o A168183 (Magma) [n+Floor((n-1)/8) : n in [1..100]]; // _Wesley Ivan Hurt_, Sep 12 2015
%o A168183 (Python) from gmpy2 import f_mod
%o A168183 [n for n in range(100) if f_mod(n,9)] # _Bruno Berselli_, Dec 05 2016
%Y A168183 Complement of A008591.
%Y A168183 Cf. A010887, A010888, A109012, A168182, A248375.
%K A168183 nonn,easy
%O A168183 1,2
%A A168183 _Reinhard Zumkeller_, Nov 30 2009