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%I #9 Aug 03 2017 01:34:28
%S 1,4,17,52,160,469,1337,3750,10347,28249,76382,204996,546651,1449952,
%T 3828232,10067585,26384939,68941126,179658343,467084601,1211812016,
%U 3138075544,8112667259,20941558268,53983767498
%N Greek-key tours on a 4 X n board; i.e., self-avoiding walks on 4 X n grid starting in top left corner.
%D Posting by Thomas Womack (mert0236(AT)sable.ox.ac.uk) to sci.math newsgroup, Apr 21 1999.
%F Conjecture: a(n)=3a(n-1)+3a(n-2)-9a(n-3)-6a(n-4)+5a(n-5)+a(n-6)-3a(n-7)+a(n-8) for n>=10. - _Dean Hickerson_, Apr 05 2003
%F Conjecture: G.f.: x*(-(x-1)*(x^7-x^6-2*x^5+3*x^4-2*x^3-4*x^2-2*x-1))/((x^4-2*x^3+2*x^2+2*x-1)*(x^4-x^3-3*x^2-x+1)) [From Maksym Voznyy (voznyy(AT)mail.ru), Jul 27 2009]
%Y Cf. A046994.
%K nonn,walk
%O 1,2
%A Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr)
%E More terms from _Hugo van der Sanden_, Apr 02 2003
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