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%I #15 Apr 24 2024 14:18:56
%S 13,23,-1,43,53,-1,73,83,-1,103,113,-1,1333333333333333,1433,-1,163,
%T 173,-1,193,20333,-1,223,233,-1,2533333333,263,-1,283,293,-1,313,
%U 323333,-1,3433,353,-1,373,383,-1
%N Smallest prime obtained by appending one or more 3's to n, or -1 if no such prime exists.
%C Next term is 40 followed by 483 3's and is too large to display here (see the b-file).
%H Toshitaka Suzuki, <a href="/A372056/b372056.txt">Table of n, a(n) for n = 1..409</a>
%e For n = 13, a(13) = 1333333333333333 is a prime (but 133,1333,13333 etc. are not primes).
%Y See A112394 for another version.
%Y Cf. A090584, A112386, A113076.
%K base,sign,new
%O 1,1
%A _Toshitaka Suzuki_, Mar 30 2024
%E Edited by _N. J. A. Sloane_, Apr 24 2024
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