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 A234471 #49 Jan 06 2015 22:59:09 %S A234471 0,0,0,2,10,30,86,180,344,624,1056,1626,2522,3646,5118,7164,9784, %T A234471 12868,16848,21438,27202,34298,42550,51800,63184,76256,91032,108086, %U A234471 127850,149442,174902,202552,233608,268512,306664,349394,398226,450510,507038,569204 %N A234471 Number of sets of 4 distinct collinear points in an n X n permutation array in which leftmost pair has same spacing as rightmost pair. %C A234471 Configuration of points forms a degenerate parallelogram. %H A234471 Chris Swanson, Randy Ho, Bill Correll, Jr, <a href="/A234471/b234471.txt">Table of n, a(n) for n = 1..1000</a> %Y A234471 Cf. A243643. %K A234471 nonn %O A234471 1,4 %A A234471 _Christopher N. Swanson_, Randy Ho, and _Bill Correll, Jr._, Jun 08 2014