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%I #10 Feb 07 2017 17:27:45
%S 1,441,614581,1064557805,1949314526229,3619365754064658,
%T 6743148875847013949,12573396789552627635974,
%U 23449283563696481324707977,43734844458505039459034141789,81570040233489554572733439665568,152137050633841639720340771054558899
%N Number of tilings of a 7 X 3n rectangle using 7n trominoes of any shape.
%H Alois P. Heinz, <a href="/A233343/b233343.txt">Table of n, a(n) for n = 0..300</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Tromino">Tromino</a>
%Y Trisection of column k=7 of A233320.
%K nonn
%O 0,2
%A _Alois P. Heinz_, Dec 07 2013