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%I #15 Oct 02 2017 21:30:23
%S 1,15,111,649,3495,18189,93231,474479,2406621,12187137,61668609,
%T 311938233,1577602849,7977940187,40342860995,204001993697,
%U 1031568839407,5216271035257,26376744398811,133377264694375
%N Not necessarily symmetric n X 3 crossword puzzle grids.
%H Andrew Howroyd, <a href="/A034184/b034184.txt">Table of n, a(n) for n = 1..200</a>
%F Appears to obey a 9-term linear recurrence. - _Ralf Stephan_, May 05 2004
%F Empirical g.f.: -x*(x^8-x^7-2*x^6-9*x^5+14*x^4-11*x^3-6*x^2+5*x+1) / ((x-1)*(x^2+2*x-1)*(x^6-7*x^5+x^4+6*x^3-11*x^2+7*x-1)). - _Colin Barker_, Jun 09 2013
%Y Row 3 of A292357.
%Y Column sums of A059679.
%Y Cf. A001333, A034182, A034184, A034185, A034186, A034187.
%K nonn
%O 1,2
%A _Erich Friedman_
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