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A005747 Number of n-covers of an unlabeled 6-set.
(Formerly M5018)
5

%I M5018 #22 Feb 28 2023 22:25:11

%S 1,16,196,2197,22952,223034,2004975,16642937,127654604,907349654,

%T 6000728764,37093282121,215296646264,1178514299094,6108871834312,

%U 30098215339608,141433252447082,635816643771438,2742163498527536,11374522802412498,45482770393453638

%N Number of n-covers of an unlabeled 6-set.

%C Number of n X 6 binary matrices with at least one 1 in every column up to row and column permutations. - _Andrew Howroyd_, Feb 28 2023

%D R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Andrew Howroyd, <a href="/A005747/b005747.txt">Table of n, a(n) for n = 1..1000</a>

%H Vladeta Jovovic, <a href="/A005748/a005748.pdf">Binary matrices up to row and column permutations</a>

%o (PARI) Vec((G(6, x) - G(5, x)) + O(x^30)) \\ G defined in A028657. - _Andrew Howroyd_, Feb 28 2023

%Y A diagonal of A055080.

%Y First differences give A055084.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, _Simon Plouffe_

%E Corrected and extended by _Vladeta Jovovic_, Jun 13 2000

%E Terms a(20) and beyond from _Andrew Howroyd_, Feb 28 2023

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)