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Template:Sequence of the Day for December 10

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Intended for: December 10, 2012

Timetable

  • First draft entered by Alonso del Arte on December 7, 2011 based on remarks by Piet Hut ✓
  • Draft to be reviewed by October 10, 2011
  • Draft to be approved by November 10, 2011
Yesterday's SOTD * Tomorrow's SOTD

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A001190: Wedderburn–Etherington numbers: binary rooted trees (every node has out-degree 0 or 2) with
n
endpoints (and
2 n  −  1
nodes in all).
{ 1, 1, 1, 2, 3, 6, 11, 23, 46, 98, ... }
This is also the number of ways to place
n
stars in a single bound stable hierarchical multiple star system; i.e. taking only the configurations from A003214 where all stars are included in single outer parentheses.