%I #9 Dec 10 2016 14:34:07
%S 1,2,6,19,61,197,640,2091,6860,22566,74365,245397,810639,2680025,
%T 8865866
%N Number of prefix-closed polyominoes of area n.
%H Enrico Formenti and Paolo Massazza, <a href="https://www.researchgate.net/publication/303836692_From_Tetris_to_polyominoes_generation">From Tetris to Polyominoes Generation</a>, Proceedings of GASCom 2016 conference, 2016.
%Y Cf. A000105, A001168.
%K nonn,more
%O 1,2
%A _Enrico Formenti_, Aug 13 2016