A071110 a(n) is the smallest integer >=0 we cannot obtain from n, n+1, n+2, n+3, n+4 and the operators +, -, *, /, using each number only once.

29, 76, 141, 172, 193, 197, 205, 211, 245, 181, 162, 85, 86, 69, 71, 61, 62, 67, 52, 53, 58, 58, 58, 59, 62, 45, 46, 49, 20, 51, 7, 22, 10, 7, 10, 7, 7, 7, 7, 15, 12, 13, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 10, 7, 7, 7, 7, 7, 7, 10, 7, 7, 7, 7, 7, 7, 7, 7, 7

Offset: 0

Author

Koksal Karakus (karakusk(AT)hotmail.com), May 27 2002

Keywords

• nonn

Comments

It seems that a(n)=7 for all n>=62, but this needs to be proved.

Examples

			a(61)=10 because by using 61, 62, 63, 64, 65 we can get 62-61=1, 63-61=2, ..., 63/((64-61)*(65-62))=7, (65-61)*(64+62)/63=8, (65-62)*(64-61)=9 but we cannot obtain 10 in the same way.
a(32) != 7 because 7 = 35 / (34 - (32 - (36 - 33))). - _Sean A. Irvine_, Jun 30 2024
		

Links

• Gilles Bannay, Countdown Problem

Crossrefs

Cf. A060316.

Extensions

a(32) and a(40) corrected by Sean A. Irvine, Jun 30 2024