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 A071985 a(n) is the smallest positive integer that cannot be obtained using at most n-1 of the integers {1, 2, ..., n} using each number at most once and the operators +, -, *, /. 0
 1, 3, 7, 17, 47, 158, 681, 3209, 17989, 104289 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For all n>=2, A060315(n+1) > a(n) > A060315(n). LINKS G. Bannay, LE COMPTE EST BON EXAMPLE a(3)=7 because using two of the numbers {1,2,3} with the four operations we can obtain 1=1, 2=2, 3=3, 3+1=4, 3+2=5, 3*2=6 but we cannot obtain 7 in the same way. CROSSREFS Cf. A060315. Sequence in context: A320774 A151265 A179944 * A181419 A090977 A324789 Adjacent sequences:  A071982 A071983 A071984 * A071986 A071987 A071988 KEYWORD hard,more,nonn AUTHOR Koksal Karakus (karakusk(AT)hotmail.com), Jun 17 2002 STATUS approved

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Last modified July 23 12:19 EDT 2021. Contains 346259 sequences. (Running on oeis4.)