A319323 a(n) is the number of column convex polyiamonds with n cells.

2, 3, 6, 14, 36, 94, 246, 645, 1682, 4367, 11312, 29261, 75654, 195607, 505794, 1307977, 3382628, 8748288, 22625594, 58516858, 151343298, 391422104, 1012341602

Offset: 1

Author

David Bevan, Sep 27 2018

Keywords

• nonn
• more

Comments

A polyiamond is column convex if the intersection of its interior with any vertical line through the centers of the cells is connected.

Examples

			The only septiamonds that are not column convex are four rotations/reflections of a "7" shape. So a(7) = A001420(7) - 4 = 246.
		

Links

• Adam Gruber, Java program to count lattice animals.

Crossrefs

Cf. A001420 (fixed polyiamonds), A238823 (row convex polyiamonds).