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 A183264 #8 May 12 2020 19:56:37 %S A183264 0,2,15,64,220,672,1904,5120,13248,33280,81664,196608,465920,1089536, %T A183264 2519040,5767168,13090816,29491200,65994752,146800640,324796416, %U A183264 715128832,1567621120,3422552064,7444889600,16139681792,34879832064,75161927680,161531035648,346281738240 %N A183264 Number of singly defective permutations of 1..n with exactly 1 maximum. %C A183264 A singly defective permutation omits one value and repeats another value. %C A183264 a(1) is zero because there are no defective permutations of a single element. %H A183264 Andrew Howroyd, <a href="/A183264/b183264.txt">Table of n, a(n) for n = 1..500</a> %F A183264 Conjecture: a(n) = n * (3*n-4) * 2^(n-3) for n > 1. - _Andrew Howroyd_, May 12 2020 %e A183264 Some solutions for n=3 with 1 maximum: %e A183264 (3,3,2) (1,3,3) (1,1,2) (2,1,1) (3,3,1) (1,3,1) (1,2,2) (2,2,1) (2,2,3). %Y A183264 Column 1 of A183270. %Y A183264 Cf. A053220. %K A183264 nonn %O A183264 1,2 %A A183264 _R. H. Hardin_, Jan 03 2011 %E A183264 Terms a(16) and beyond from _Andrew Howroyd_, May 12 2020