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 A210323 #25 Oct 18 2014 11:05:04 %S A210323 0,3,16,57,192,599,1872,5727,17488,53115,161040,487073,1471680, %T A210323 4441167,13392272,40355877,121543680,365895947,1101089808,3312442185, %U A210323 9962240928,29954639751,90049997136,270661616363,813397065024,2444101696683,7343167947040,22059763982001,66263812628160 %N A210323 Number of 2-divided words of length n over a 3-letter alphabet. %C A210323 See A210109 for further information. %C A210323 It appears that A027376 gives the number of 2-divided words that have a unique division into two parts. - _David Scambler_, Mar 21 2012 %C A210323 Row sums of the following irregular triangle W(n,k) which shows how many words of length n over a 3-letter alphabet are 2-divided in k>=1 different ways (3-letter analog of A209919): %C A210323 3; %C A210323 8, 8; %C A210323 18, 21, 18; %C A210323 48, 48, 48, 48; %C A210323 116, 124, 119, 124, 116; %C A210323 312, 312, 312, 312, 312, 312; %C A210323 810, 828, 810, 831, 810, 828, 810; %C A210323 2184, 2184, 2192, 2184, 2184, 2192, 2184, 2184; %C A210323 5880, 5928, 5880, 5928, 5883, 5928, 5880, 5928, 5880; %C A210323 First column of the following triangle D(n,k) which shows how many words of length n over a 3-letter alphabet are k-divided: %C A210323 3; %C A210323 16, 1; %C A210323 57, 16, 0; %C A210323 192, 78, 6, 0; %C A210323 599, 324, 56, 0, 0; %C A210323 1872, 1141, 343, 15, 0, 0; %C A210323 5727, 3885, 1534, 166, 0, 0, 0; %C A210323 17488, 12630, 6067, 1135, 20, 0, 0, 0; %C A210323 53115, 40315, 22162, 5865, 351, 0, 0, 0, 0; %C A210323 161040, 126604, ... %C A210323 - _R. J. Mathar_, Mar 25 2012 %C A210323 Speculation: W(2n+1,2)=W(2n+1,1) and W(2n,2) = W(2n,1)+W(n,1). W(3n+1,3)=W(3n+1,1); W(3n+2,3)=W(3n+1,1); W(3n,3) = W(3n,1)+W(n,1). - _R. J. Mathar_, Mar 27 2012 %F A210323 a(n) = 3^n - A001867(n) (see A209970 for proof). %Y A210323 Cf. A210109, A209970, A001867. %K A210323 nonn %O A210323 1,2 %A A210323 _N. J. A. Sloane_, Mar 20 2012 %E A210323 a(1)-a(12) computed by _David Scambler_, Mar 19 2012; a(13) onwards from _N. J. A. Sloane_, Mar 20 2012