The OEIS is supported by the many generous donors to the OEIS Foundation.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #12 Mar 28 2018 08:13:50
%S 1,6,13,26,72,175,407,1005,2450,5893,14318,34780,84221,204245,495483,
%T 1201256,2912843,7064014,17129250,41536473,100724269,244248135,
%U 592280544,1436238121,3482767494,8445435610,20479537209,49661306333,120424822297
%N Number of n X 5 binary arrays with each 1 adjacent to exactly one 1 vertically and one 1 horizontally.
%C Equivalent to all 1s connected only in 2 X 2 blocks.
%C Column 5 of A183342.
%H R. H. Hardin, <a href="/A183337/b183337.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = a(n-1) + a(n-2) + 5*a(n-3) + 2*a(n-4) + a(n-5) - a(n-7) - a(n-8).
%F Empirical g.f.: x*(1 + 5*x + 6*x^2 + 2*x^3 + x^4 - x^5 - 2*x^6 - x^7) / (1 - x - x^2 - 5*x^3 - 2*x^4 - x^5 + x^7 + x^8). - _Colin Barker_, Mar 27 2018
%e Some solutions for 7 X 5:
%e 1 1 0 0 0 0 0 0 1 1 0 0 1 1 0 0 0 1 1 0
%e 1 1 0 0 0 0 0 0 1 1 0 0 1 1 0 0 0 1 1 0
%e 0 0 1 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0
%e 0 0 1 1 0 0 0 0 0 0 1 1 0 0 0 1 1 0 1 1
%e 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 1 0 1 1
%e 1 1 0 0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0 0
%e 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0
%Y Cf. A183342.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 04 2011