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 A087328 #13 Jul 18 2020 10:04:00 %S A087328 1,3,4,4,9,12,15,16,22,27,31,36,43,51,58,64,75,83,93,100,112,123,133, %T A087328 144,157,171,184,196,213,227,243,256,274,291,307,324,343,363,382,400, %U A087328 423,443,465,484,508,531,553,576,601,627,652,676,705,731,759,784,814 %N A087328 Independence numbers for KT_3 knight on hexagonal board. %H A087328 Colin Barker, <a href="/A087328/b087328.txt">Table of n, a(n) for n = 1..1000</a> %H A087328 J.-P. Bode and H. Harborth, <a href="https://doi.org/10.1016/S0012-365X(03)00181-X">Independence for knights on hexagon and triangle boards</a>, Discrete Math., 272 (2003), 27-35. %H A087328 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-2,1,0,-1,2,0,-2,1). %F A087328 a(n) = ceiling(n^2/4) if n == 0, 1, 4, 8, 11 (mod 12), ceiling(n^2/4) + 1 if n == 3, 9 (mod 12) and ceiling(n^2/4) + 2 if n == 2, 5, 6, 7, 10 (mod 12) and n != 6. %F A087328 G.f.: x*(1+x-2*x^2-2*x^3+6*x^4-x^5-4*x^6+x^7+3*x^8-x^9+x^11-2*x^12+2*x^14-x^15) / ((1-x)^3*(1+x)*(1+x^2)*(1-x^2+x^4)). - _Colin Barker_, Feb 02 2016 %o A087328 (PARI) Vec(x*(1+x-2*x^2-2*x^3+6*x^4-x^5-4*x^6+x^7+3*x^8-x^9+x^11-2*x^12+2*x^14-x^15)/((1-x)^3*(1+x)*(1+x^2)*(1-x^2+x^4)) + O(x^100)) \\ _Colin Barker_, Feb 02 2016 %Y A087328 Cf. A087327, A087329. %K A087328 nonn,easy %O A087328 1,2 %A A087328 _N. J. A. Sloane_, Oct 21 2003 %E A087328 More terms from _David Wasserman_, May 06 2005