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.

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

Sequence in context: A005508 A110448 A064450 this_sequence A072847 A095895 A051934

Adjacent sequences: A130620 A130621 A130622 this_sequence A130624 A130625 A130626

hard,more,nonn

Tanya Khovanova (tanyakh(AT)yahoo.com), Aug 11 2007