1,2

I had written a C++ program to find the smallest positive integer that cannot be obtained from the integers {1,2,...,n-1} using each number exactly once and the operators +,-,*,/. The result is same as this sequence. It takes the program two days to find the result for n=11. We still don't know whether the two sequences are same for n greater than 11. [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Oct 01 2008]

The first 12 items are the same as the result of using all number from 0 to n-1 exactly once and only the operators +,-,* (So we could get all integers less than a(n) without the operator /). The minimal number which could not be reached using all numbers from 0 to 12 exactly once and only operators +,-,* is 10539427. But I have still not verified whether it is a(13) [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Oct 08 2008]

The 13th item has now been verified by computer [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Nov 05 2008]

G. Bannay, LE COMPTE EST BON (to obtain a(4)=10 for example, enter ceb -a4 -x1 0 1 2 3)

Index entries for similar sequences

The C++ source code to find the smallest integer [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Oct 01 2008]

Du, Zhao Hui, The webpage where the result is posted [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Oct 08 2008]

Link to the result [From Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Nov 05 2008]

For n=4 we have {0,1,2,3} to play with and we can get 6=2*3, 7=2*3+1, 8=2*(1+3), 9=3*(1+2), but we cannot get 10, hence a(4) = 10.

Cf. A060316.

Cf. A141494.

Sequence in context: A003223 A061417 A153921 this_sequence A148111 A148112 A148113

Adjacent sequences: A060312 A060313 A060314 this_sequence A060316 A060317 A060318

hard,nonn

Jean-Marc Rebert (jm.rebert(AT)calixo.net), Mar 28 2001

More terms from Koksal Karakus (karakusk(AT)hotmail.com), May 26 2002

One more term from Du, Zhao Hui (zhao.hui.du(AT)gmail.com), Oct 08 2008