A319321 a(n) is the number of d+/d- diagonally convex polyplets (polyominoes which need only touch at corners) with n cells.

1, 4, 20, 108, 600, 3368, 18968, 106906, 602532, 3395402, 19131460, 107788900, 607274848

Offset

1,2

Comments

A polyplet is d+ [d-] diagonally convex if the intersection of its interior with any line of slope 1 [-1] through the centers of the cells is connected.

Links

Table of n, a(n) for n=1..13.

Adam Gruber, Java program to count lattice animals.

Example

The only tetraplets that are not d+ diagonally convex are two animals consisting of a horizontal domino and a vertical domino joined at a corner. So a(4) = A006770(4) - 2 = 108.

Crossrefs

Cf. A006770 (fixed polyplets), A187077 (row convex polyplets), A187276 (d+/d- diagonally convex polyominoes).

Sequence in context: A263965 A265084 A321111 * A321574 A225621 A375303

Adjacent sequences: A319318 A319319 A319320 * A319322 A319323 A319324

Keyword

nonn,more

Author

David Bevan, Sep 27 2018

Status

approved