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%I #8 Jan 07 2022 13:03:49
%S 1,3,4,13,25,72,166,450,1124,2973,7603,19865,51199,132982,343290,
%T 888309,2292325,5918742,15258937,39329418
%N Number of 2-sided strip polytans with n cells.
%H Ed Pegg, Jr., <a href="http://demonstrations.wolfram.com/PolyformExplorer/">Illustrations of polyforms</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Polytan.html">Polytan</a>
%Y Cf. A006074, A151520.
%K nonn,hard,more
%O 1,2
%A _Ed Pegg Jr_, May 13 2009
%E a(6)-a(20) from _John Mason_, Jan 07 2022