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 A116903 Seaweeds(n): number of n-step self-avoiding walks on upper two quadrants grid starting at origin. 13
 1, 3, 7, 19, 49, 131, 339, 899, 2345, 6199, 16225, 42811, 112285, 296051, 777411, 2049025, 5384855, 14190509, 37313977, 98324565, 258654441, 681552747, 1793492411, 4725856129, 12439233695, 32778031159, 86295460555, 227399388019, 598784536563, 1577923781445, 4155176578581 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS These walks remind me of fluctuant seaweeds anchored to the sea bottom. LINKS M. N. Barber et al., Some tests of scaling theory for a self-avoiding walk attached to a surface, 1978 J. Phys. A: Math. Gen. 11 1833. [Vladeta Jovovic, Nov 26 2008] EXAMPLE The 19 seaweeds of length 3. X marks the origin = anchor point. ........................................................ O-O-O...O-O.. .O-O...O-O....O..O-O-O...O......O..O-O.... ....|.....|.. .|.....|......|..|.......|......|....|.... ....X...X-O....O.....O-X....O..X..O-O..O-O....O....O-X.. ...............|............|.......|....|....|......... O-O.....O-O....X....O.......O..O....O....X..X-O.......O. |.|.....|...........|.......|..|....|.................|. X.O...X-O.....O-O...O-O-X...X..O....X.....O.........O-O. ..............|.|..............|..........|.........|... ..X-O-O-O.....O.X...O-O-O-X....O-X....X-O-O.........X... ........................................................ CROSSREFS Cf. A001411, A038373, A116903. Sequence in context: A061646 A017926 A017927 * A298416 A151266 A147234 Adjacent sequences:  A116900 A116901 A116902 * A116904 A116905 A116906 KEYWORD nonn AUTHOR Giovanni Resta, Feb 15 2006 EXTENSIONS a(23)-a(30) from Scott R. Shannon, Jul 26 2020 STATUS approved

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Last modified November 28 13:18 EST 2020. Contains 338724 sequences. (Running on oeis4.)