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 A140770 #5 Dec 16 2016 04:12:41 %S A140770 1,16,289,4624,67081,902500,11471769,139570596,1640493009,18754206916, %T A140770 209576262025,2298031637476,24798178969729,263962539461776, %U A140770 2776718023652329,28909790108979264,298278580556192769,3052900712959977636,31023767417676585561,313247762072931012804 %N A140770 3D analog of A081113: the number of (n-1)-step paths a 3D chess king can make starting from one face of the n X n X n cube to the opposite one. %C A140770 The rule is that the king can move in one step to any of the 26 (=3*3-1) adjacent positions; because we allow only solutions with n-1 steps, one component of the direction is enforced and only a choice of 9 different next steps remains; if the path is close to the cube surface, even fewer. %C A140770 This is the square of A081113, because for both x and y coordinates you have A081113(n) possibilities for the path (and you can choose them independently). - _Robert Gerbicz_, Jun 11 2010 %e A140770 Example: for n=2, we can start from any of the 4 places on one face and move from there directly to any of the 4 positions on the opposite side: a(2) = 4*4 = 16. %Y A140770 Cf. A081113. %K A140770 nonn %O A140770 1,2 %A A140770 _R. J. Mathar_, Jun 11 2010