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%I M2182 #18 Mar 06 2020 23:19:08
%S 0,2,168,32738,20825760,47942081642
%N The number of n X n (0,1)-matrices with a 1-width of 2.
%C Determining the 1-width of a matrix is NP-complete. - _Sean A. Irvine_, Mar 06 2020
%D Lam, Clement W. H. The distribution of 1-widths of (0, 1)-matrices. Discrete Math. 20 (1977/78), no. 2, 109-122.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a005/A005020.java">Java program</a> (github)
%H <a href="/index/Mat#binmat">Index entries for sequences related to binary matrices</a>
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E a(1) corrected and title improved by _Sean A. Irvine_, Mar 06 2020
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