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 A007887 #34 Jul 08 2025 01:02:04
%S A007887 0,1,1,2,3,5,8,4,3,7,1,8,0,8,8,7,6,4,1,5,6,2,8,1,0,1,1,2,3,5,8,4,3,7,
%T A007887 1,8,0,8,8,7,6,4,1,5,6,2,8,1,0,1,1,2,3,5,8,4,3,7,1,8,0,8,8,7,6,4,1,5,
%U A007887 6,2,8,1,0,1,1,2,3,5,8,4,3
%N A007887 a(n) = Fibonacci(n) mod 9.
%H A007887 Vincenzo Librandi, <a href="/A007887/b007887.txt">Table of n, a(n) for n = 0..1000</a>
%H A007887 G. Wulczy, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Scanned/13-1/advanced13-1.pdf">Unity with Fibonacci, Problem H-247 and solution</a>, Fib. Quarter. p. 89_90, Vol 15, 1, Feb. 1977. Mentions this sequence.
%H A007887 <a href="/index/Rec#order_24">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%F A007887 Period 24 = A001175(9). Proof: F_{n+24} = F_n + 9*(5152 F_{n+1} + 3184 F_n). - Olivier Wittenberg, following a conjecture by _Ralf Stephan_, Sep 28 2004
%F A007887 The numbers have period 24 since F_{n+24} = F_n + 9*(5152 F_{n+1} + 3184 F_n). - Olivier Wittenberg, Sep 28 2004
%t A007887 Mod[Fibonacci[Range[0,80]],9] (* _Harvey P. Dale_, Mar 23 2012 *)
%o A007887 (Magma) [Fibonacci(n) mod 9: n in [0..100]]; // _Vincenzo Librandi_, Feb 04 2014
%o A007887 (PARI) a(n)=fibonacci(n)%9 \\ _Charles R Greathouse IV_, Oct 07 2015
%K A007887 nonn,easy
%O A007887 0,4
%A A007887 _N. J. A. Sloane_