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 A005745 M4156 #22 Feb 28 2023 22:25:19 %S A005745 1,6,23,65,156,336,664,1229,2159,3629,5877,9221,14070,20951,30530, %T A005745 43634,61283,84725,115461,155294,206368,271210,352784,454550,580509, %U A005745 735280,924163,1153207,1429292,1760218,2154776,2622859,3175555,3825247 %N A005745 Number of n-covers of an unlabeled 3-set. %C A005745 Number of n X 3 binary matrices with at least one 1 in every column up to row and column permutations. - _Andrew Howroyd_, Feb 28 2023 %D A005745 R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152. %D A005745 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A005745 Andrew Howroyd, <a href="/A005745/b005745.txt">Table of n, a(n) for n = 1..1000</a> %H A005745 Vladeta Jovovic, <a href="/A005748/a005748.pdf">Binary matrices up to row and column permutations</a> %F A005745 a(n) = A002727(n) - A002623(n). %F A005745 G.f.: -x*(x^8-x^7-x^6-2*x^5+2*x^4+x^3-3*x^2-2*x-1)/((x^3-1)^2*(x^2-1)^2*(x-1)^4). %o A005745 (PARI) Vec(G(3, x) - G(2, x) + O(x^40)) \\ G defined in A028657. - _Andrew Howroyd_, Feb 28 2023 %Y A005745 A diagonal of A055080. %Y A005745 First differences give A055609. %Y A005745 Cf. A002623, A002727. %Y A005745 Cf. A005744, A005746, A005747, A005748, A005771. %K A005745 easy,nonn %O A005745 1,2 %A A005745 _N. J. A. Sloane_, _Simon Plouffe_ %E A005745 More terms from _Vladeta Jovovic_, May 26 2000