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A071997
a(n) is the smallest positive integer that cannot be obtained by using the number 2 at most n times and the operators +, -, *, /.
1
1, 3, 5, 7, 11, 19, 27, 43, 75, 115, 171, 307, 555, 691, 1383, 2467, 3627, 7243, 10995, 17587, 28973, 57943, 87963, 136627, 267573, 465293, 807629, 1407093, 2390667, 4216531, 7122293, 11245133, 21756267, 39652589
OFFSET
1,2
EXAMPLE
a(3)=5 because using 2 at most thrice we can get 2/2=1, 2=2, 2+(2/2)=3, 2+2=4, but we cannot obtain 5 in the same way.
CROSSREFS
Cf. A048175.
Sequence in context: A082603 A362250 A161420 * A093442 A364920 A155008
KEYWORD
nonn,hard,more
AUTHOR
Koksal Karakus (karakusk(AT)hotmail.com), Jun 17 2002
EXTENSIONS
a(18)-a(34) from Austin T. Mohr, May 17 2021
STATUS
approved