A057729 - OEIS

%I #18 Jul 27 2021 04:00:57

%S 0,0,1,1,1,4,5,16,37,120,345,1181,3844,13429,46736,167172

%N Number of triangular polyominoes (or polyiamonds) [A000577] with perimeter n.

%D a(10) found by Brendan Owen.

%H Andrew Clarke, <a href="http://www.recmath.com/PolyPages/PolyPages/Isopoly1s.html">Isometrical Polyiamonds</a>

%H <a href="/A057729/a057729.gif">Picture from Andrew Clarke's page showing the 4 polyiamonds of perimeter 6 and the 5 of perimeter 7.</a>

%Y Cf. A000577, A284869, A316196.

%K nonn,nice,more

%O 1,6

%A _N. J. A. Sloane_, Oct 29 2000

%E Link updated by _William Rex Marshall_, Dec 16 2009

%E a(11)-a(12) from _Luca Petrone_, Apr 04 2017

%E a(12)-a(16) corrected and extended by _John Mason_, Jul 26 2021