1,3

2n+2 is the maximal perimeter of an n-celled polyomino. a(n) is the number of n-celled polyominoes that have a tree as their connectedness graph (vertices of this graph correspond to cells, and two vertices are connected if the corresponding cells have a common edge)

Isoperimetrical Polyominoes

Poly Pages

a(n) <= A000105(n), a(n) <= A057730(n+1).

Sequence in context: A071314 A123441 A086441 this_sequence A099412 A100094 A099525

Adjacent sequences: A131479 A131480 A131481 this_sequence A131483 A131484 A131485

hard,more,nonn

Tanya Khovanova (tanyakh(AT)yahoo.com), Jul 27 2007