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

1,1

Comments

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

Links

Table of n, a(n) for n=1..23.

Adam Gruber, Java program to count lattice animals.

Example

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

Crossrefs

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

Sequence in context: A246640 A080408 A275774 * A341630 A001420 A337186

Adjacent sequences: A319320 A319321 A319322 * A319324 A319325 A319326

Keyword

nonn,more

Author

David Bevan, Sep 27 2018

Status

approved