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 A342537 Number of free polyominoes with n cells having simply-connected interiors. 4
 1, 1, 2, 5, 12, 35, 108, 368, 1283, 4639, 17003, 63222, 236819, 893515, 3387953, 12904855, 49335965, 189243115 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The polyominoes referred to in the definition are those having a single traceable perimeter. The definition therefore includes the heptomino with a hole, as in this case the border, although not self-avoiding (it meets itself at a corner) is still traceable; it excludes the square octomino with a hole, whose border consists of two distinct polygons. Thus starting from n=8, A000104(n) < a(n) < A000105(n). LINKS Table of n, a(n) for n=1..18. CROSSREFS Cf. A000104 (free polyominoes without holes), A000105 (free polyominoes). Sequence in context: A148287 A036357 A000104 * A000105 A055192 A108555 Adjacent sequences: A342534 A342535 A342536 * A342538 A342539 A342540 KEYWORD nonn,more AUTHOR John Mason, Allan C. Wechsler, Mar 15 2021 EXTENSIONS a(17)-a(18) from John Mason, Jan 04 2023 STATUS approved

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Last modified November 30 19:52 EST 2023. Contains 367462 sequences. (Running on oeis4.)