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 A049463 Number of basic interval orders of length n. 0
 1, 2, 7, 34, 219, 1787, 17936, 216169, 3069552, 50562672, 953877927, 20389082457, 489301660818, 13080166471127, 386841424466953, 12581201258360820, 447574544428423114, 17333939484785264282, 727718718839603466267 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS One may represent a basic length n interval order using n distinct endpoints. The removal of any element from such an order yields an interval order with shorter length. REFERENCES Amy N. Myers, Results in Enumeration and Topolgoy of Interval Orders, Ph.D. Thesis at Dartmouth College. Amy N. Myers, Basic Interval Orders, Order, Volume: 16, Issue: 3, 1999, pp. 261-275. LINKS FORMULA A recurrence in three variables exists. EXAMPLE a(2)=1 since {[ 1,1 ],[ 2,2 ]} is the unique basic interval order with two distinct endpoints. CROSSREFS Sequence in context: A185324 A135882 A143740 * A029894 A110313 A000944 Adjacent sequences:  A049460 A049461 A049462 * A049464 A049465 A049466 KEYWORD nonn,nice,easy AUTHOR Amy N. Myers (Amy.Myers(AT)Alum.Dartmouth.ORG) STATUS approved

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