%N First differences of corner sequence A256536 associated with A151723.
%C Number of cells turned ON at n-th stage in one of the outside corners of an infinite hexagon-shaped structure on hexagonal grid.
%C For an animation see "The movie version" in Links section.
%H David Applegate, <a href="/A139250/a139250.anim.html">The movie version</a>
%H N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a>
%H <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a>
%F a(1) = 1; a(2) = 3.
%F It appears that a(n) = 1 + ((A151724(n) + A151724(n-1))/3, n >= 3.
%F It appears that a(n) = 1 + ((A151723(n) - A151723(n-2))/3, n >= 3.
%F It appears that a(n) = 1 + 2*(A170898(n-2) + A170898(n-3)), n >= 3.
%F a(3) = 5.
%F It appears that a(n) = 1 + 2*(A169779(n-2) - A169779(n-4)), n >= 4.
%e Written as an irregular triangle in which the row lengths are the absolute values of the terms of A141531, the sequence begins:
%e 9, 9;
%e 9,17,29,37,37,53,85,85,49,41,73,101, 93,101,125, 65;
%e It appears that the right border gives A083318, whose representation in base 2 gives A000533.
%Y Cf. A000533, A083318, A141531, A151723, A151724, A169779, A170898, A256536.
%A _Omar E. Pol_, Apr 02 2015