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 A154811 #33 Feb 21 2024 01:47:50 %S A154811 1,2,5,4,7,8,8,7,4,5,2,1,1,2,5,4,7,8,8,7,4,5,2,1,1,2,5,4,7,8,8,7,4,5, %T A154811 2,1,1,2,5,4,7,8,8,7,4,5,2,1,1,2,5,4,7,8,8,7,4,5,2,1,1,2,5,4,7,8,8,7, %U A154811 4,5,2,1 %N A154811 a(n) = Fibonacci(2*n+1) mod 9. %C A154811 Periodic with period length 12. %H A154811 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,-1,1). %F A154811 a(n) = A001519(n+1) mod 9 = A122367(n) mod 9 = |A099496(n)| mod 9. %F A154811 From _R. J. Mathar_, Apr 10 2009: (Start) %F A154811 a(n) = a(n-1) - a(n-6) + a(n-7). %F A154811 G.f.: -(1 + x + 3*x^2 - x^3 + 3*x^4 + x^5 + x^6)/((x - 1)*(x^2 + 1)*(x^4 - x^2 + 1)). (End) %t A154811 Mod[Fibonacci[Range[1,151,2]],9] (* _Harvey P. Dale_, Jul 10 2018 *) %o A154811 (PARI) a(n)=fibonacci(n%12*2+1)%9 \\ _Charles R Greathouse IV_, Dec 21 2011 %Y A154811 Cf. A010689, A010875. %K A154811 nonn,easy %O A154811 0,2 %A A154811 _Paul Curtz_, Jan 15 2009 %E A154811 Edited by _R. J. Mathar_, Jan 23 2009 %E A154811 Typo in A-number in first formula corrected by _R. J. Mathar_, Feb 23 2009