0,5

The perimeter of a polyhex is always even. a(n) is partial sums of A057779(n) - Hexagonal polyominoes (or polyhexes, A000228) with perimeter 2n. a(2n+1) >= A131467(n) - Number of planar polyhexes (A000228) with at most n cells.

Table of n, a(n) for n=0..11.

Cf. A038142 - Number of planar cata-polyhexes with n cells.

Sequence in context: A064450 A217137 A248824 * A072847 A274371 A095895

Adjacent sequences: A130620 A130621 A130622 * A130624 A130625 A130626

hard,more,nonn

Tanya Khovanova, Aug 11 2007

approved