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 A210424 #24 May 06 2021 08:11:10 %S A210424 0,0,6,40,186,816,3396,14040,57306,233000,943608,3813000,15378716, %T A210424 61946640,249260316,1002158880,4026527706,16169288640,64901712996, %U A210424 260410648680,1044535993800,4188615723280,16792541033556,67309233561240,269746851976156 %N A210424 Number of 2-divided words of length n over a 4-letter alphabet. %C A210424 See A210109 for further information. %C A210424 It appears that A027377 gives the number of 2-divided words that have a unique division into two parts. - _David Scambler_, Mar 21 2012 %C A210424 From _R. J. Mathar_, Mar 25 2012: (Start) %C A210424 Row sums of the following table which shows how many words of length n over a 4-letter alphabet are 2-divided in k>=1 different ways: %C A210424 6; %C A210424 20, 20; %C A210424 60, 66, 60; %C A210424 204, 204, 204, 204; %C A210424 670, 690, 676, 690, 670; %C A210424 2340, 2340, 2340, 2340, 2340, 2340; %C A210424 8160, 8220, 8160, 8226, 8160, 8220, 8160; %C A210424 First column of the following triangle which shows how many words of length n over a 4-letter alphabet are k-divided: %C A210424 6; %C A210424 40, 4; %C A210424 186, 60, 1; %C A210424 816, 374, 44, 0; %C A210424 3396, 1960, 450, 12, 0; %C A210424 14040, 9103, 3175, 275, 0, 0; %C A210424 57306, 40497, 17977, 2915, 66, 0, 0; %C A210424 233000, 174127, 91326, 22243, 1318,.. %C A210424 (End) %F A210424 a(n) = 4^n - A001868(n) (see A209970 for proof). %Y A210424 Cf. A210109, A209970, A001868. %K A210424 nonn,more %O A210424 1,3 %A A210424 _N. J. A. Sloane_, Mar 21 2012 %E A210424 a(1)-a(10) computed by _R. J. Mathar_, Mar 20 2012 %E A210424 a(13) onwards from _N. J. A. Sloane_, Mar 21 2012