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A037162 Well-order the rational numbers; take denominators. 4
1, 1, 1, 1, 2, 2, 1, 1, 3, 3, 1, 1, 2, 3, 4, 4, 3, 2, 1, 1, 5, 5, 1, 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 1, 3, 5, 7, 7, 5, 3, 1, 1, 2, 4, 5, 7, 8, 8, 7, 5, 4, 2, 1, 1, 3, 7, 9, 9, 7, 3, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
REFERENCES
Sierpiński, Cardinal and Ordinal Numbers, Warsaw 1965, 2nd ed., p. 40.
LINKS
MATHEMATICA
order[n_] := Join[-Reverse[ pos = Select[(r = Range[n])/Reverse[r], Numerator[#] + Denominator[#] == n + 1 & ] ], pos]; order[0] = 0; Denominator[ Flatten[ Table[ order[n], {n, 0, 10}]]] (* Jean-François Alcover, Jun 27 2012 *)
PROG
(Haskell)
import Data.List (transpose)
import Data.Ratio ((%), denominator)
a037162 n = a037162_list !! n
a037162_list = 1 : map denominator
(concat $ concat $ transpose [map (map negate) qss, map reverse qss])
where qss = map q [1..]
q x = map (uncurry (%)) $ filter ((== 1) . uncurry gcd) $
zip (reverse zs) zs where zs = [1..x]
-- Reinhard Zumkeller, Mar 08 2013
CROSSREFS
Cf. A037161.
Cf. A038567.
Sequence in context: A050603 A286554 A352784 * A352911 A278566 A255559
KEYWORD
nonn,easy,nice,frac
AUTHOR
STATUS
approved

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Last modified March 19 06:05 EDT 2024. Contains 370952 sequences. (Running on oeis4.)