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 A322663 #13 Feb 06 2019 13:07:36 %S A322663 1,1,7,1,6,11,14,3,11,14,25,5,18,21,37,4,11,21,50,17,31,50,50,13,32, %T A322663 39,70,10,42,41,81,4,11,21,50,24,57,74,89,40,62,84,105,48,66,85,111, %U A322663 18,37,64,151,41,80,126,131,29 %N A322663 First differences of A322662 divided by 12. %C A322663 Unlike A322050, this sequence contains only finitely many 1's. However, the Cellular Automaton and its counting sequences still admit a 2^n fractal structure (Cf. A322662). The subsequences L_n = {a(2^n), a(2^n+1), ... a(2^(n+1)-1)} appear to approach a limit sequence L_{oo}, starting with 4 ON cells. Of these 4, one is a "pioneer" at distance d*2^n from the origin, with d the distance of one knight step. The other three of four ON cells are due to retrogressive growth. %F A322663 a(n) = (A322662(n)-A322662(n-1))/12. %e A322663 Written as a 2^k triangle: %e A322663 1, %e A322663 1, 7, %e A322663 1, 6, 11, 14, %e A322663 3, 11, 14, 25, 5, 18, 21, 37, %e A322663 4, 11, 21, 50, 17, 31, 50, 50, 13, 32, 39, 70, 10, 42, 41, 81, %e A322663 4, 11, 21, 50, 24, 57, 74, 89, 40, 62, 84, 105, 48, 66, 85, 111, ... %t A322663 HexStar=2*Sqrt[3]*{Cos[#*Pi/3+Pi/6],Sin[#*Pi/3+Pi/6]}&/@Range[0,5]; %t A322663 MoveSet2 =Join[2*HexStar+RotateRight[HexStar],2*HexStar+RotateLeft[HexStar]]; %t A322663 Clear@Pts;Pts[0] = {{0, 0}}; %t A322663 Pts[n_]:=Pts[n]=With[{pts=Pts[n-1]},Union[pts,Cases[Tally[Flatten[pts/.{x_,y_}:> Evaluate[{x,y}+#&/@MoveSet2],1]],{x_,1}:>x]]]; %t A322663 Abs[(1/12)*Subtract@@#&/@Partition[Length[Pts[#]]&/@Range[0,32],2,1]] %Y A322663 Hexagonal: A151724, A170898, A256537. Square: A147582, A147610, A048883; A319019, A322050, A322049. Lower Bound: A038573. %K A322663 nonn %O A322663 1,3 %A A322663 _Bradley Klee_, Dec 22 2018