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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

%I

%S 1,3,7,17,47,158,681,3209,17989,104289

%N 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 +, -, *, /.

%C For all n>=2, A060315(n+1) > a(n) > A060315(n).

%H G. Bannay, <a href="http://gilles.bannay.free.fr/jeux_us.html">LE COMPTE EST BON</a>

%H <a href="/index/Fo#4x4">Index entries for similar sequences</a>

%e 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.

%Y Cf. A060315.

%K hard,more,nonn

%O 1,2

%A Koksal Karakus (karakusk(AT)hotmail.com), Jun 17 2002

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Last modified February 23 18:13 EST 2019. Contains 320437 sequences. (Running on oeis4.)