cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A359519 Number of free polyominoes of n cells with multiply-connected interiors.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 1, 2, 16, 70, 378, 1772, 8456, 38623, 174400, 771944, 3378937
Offset: 1

Views

Author

John Mason, Jan 04 2023

Keywords

Examples

			a(8) = 1 because of:
OOO
O O
OOO

Crossrefs

Cf. A000104, A000105, A001419, A342537, A359520.

Formula

a(n) = A000105(n) - A342537(n) (all free polyominoes minus simply-connected interior polyominoes).

A359524 Number of free holey polyiamonds of n cells with simply-connected interiors.

Original entry on oeis.org

1, 4, 25, 107, 448, 1701, 6216, 21771, 74339, 248379
Offset: 9

Views

Author

John Mason, Jan 05 2023

Keywords

Crossrefs

Cf. A000577, A070764, A359520, A359523.

Formula

a(n) = A070764(n) - A359523(n).

A376496 The number of free kissing polyominoes with n cells.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 1, 5, 35, 179, 909, 4287, 19723, 88240, 388260, 1683998, 7227374, 30750236
Offset: 1

Views

Author

John Mason, Sep 25 2024

Keywords

Comments

A polyomino is 'kissing' if there exist two cells that touch only at a corner such that no cell exists touching both edgewise simultaneously.
The sequence differs from A359520 (Number of free holey polyominoes of n cells with simply-connected interiors) at a(12) because of:
OOOO OOO
O O O O OO
OOOOO OO O
OOO
which are kissing (and hence holey) but do not have simply-connected interiors.

Crossrefs

Cf. A367557, A359520.
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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