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 A057356 #24 Sep 30 2022 07:47:37
%S A057356 0,0,0,0,1,1,1,2,2,2,2,3,3,3,4,4,4,4,5,5,5,6,6,6,6,7,7,7,8,8,8,8,9,9,
%T A057356 9,10,10,10,10,11,11,11,12,12,12,12,13,13,13,14,14,14,14,15,15,15,16,
%U A057356 16,16,16,17,17,17,18,18,18,18,19,19,19,20,20,20,20,21,21,21,22,22,22
%N A057356 a(n) = floor(2*n/7).
%C A057356 The cyclic pattern (and numerator of the gf) is computed using Euclid's algorithm for GCD.
%D A057356 R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, Addison-Wesley, NY, 1994.
%D A057356 N. Dershowitz and E. M. Reingold, Calendrical Calculations, Cambridge University Press, 1997.
%H A057356 G. C. Greubel, <a href="/A057356/b057356.txt">Table of n, a(n) for n = 0..5000</a>
%H A057356 N. Dershowitz and E. M. Reingold, <a href="http://www.cs.tau.ac.il/~nachum/calendar-book/third-edition/">Calendrical Calculations Web Site</a>.
%H A057356 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,1,-1).
%F A057356 G.f.: x^4*(1+x)*(x^2-x+1)/( (x^6+x^5+x^4+x^3+x^2+x+1)*(x-1)^2 ). - Numerator corrected by _R. J. Mathar_, Feb 20 2011
%F A057356 Sum_{n>=4} (-1)^n/a(n) = Pi/4 (A003881). - _Amiram Eldar_, Sep 30 2022
%t A057356 Table[Floor[2*n/7], {n,0,50}] (* _G. C. Greubel_, Nov 03 2017 *)
%o A057356 (PARI) a(n)=2*n\7 \\ _Charles R Greathouse IV_, Sep 24 2015
%o A057356 (Magma) [Floor(2*n/7): n in [0..50]]; // _G. C. Greubel_, Nov 03 2017
%Y A057356 Floors of other ratios: A004526, A002264, A002265, A004523, A057353, A057354, A057355, A057356, A057357, A057358, A057359, A057360, A057361, A057362, A057363, A057364, A057365, A057366, A057367.
%Y A057356 Cf. A003881.
%K A057356 nonn,easy
%O A057356 0,8
%A A057356 _Mitch Harris_