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%I #26 Nov 05 2018 17:32:39
%S 1,12,123,1234,12345,123456,1234567,12345678,123456789,12345678910,
%T 1234567891011,123456789101113,12345678910111314,1234567891011131415,
%U 123456789101113141516,12345678910111314151617,1234567891011131415161718,123456789101113141516171819,12345678910111314151617181920
%N Concatenation of the numbers from 1 to n but omitting 12.
%C The first (probable) prime in this sequence is a(960) = 1234567891011131415...961 (ending in 961), found by _David Broadhurst_, Sep 28 2015.
%C No other primes through a(10000). - _Robert Price_, Nov 04 2018
%t Module[{nn=30, c}, c=Drop[Range[nn], {12}]; Table[FromDigits[Flatten[IntegerDigits/@Take[c, n]]], {n, nn - 1}]] (* _Vincenzo Librandi_, Nov 05 2018 *)
%Y Cf. A007908, A262299, A262300, A262571-A262582.
%Y See A262300 for more about this problem.
%K nonn,base
%O 1,2
%A _N. J. A. Sloane_, Sep 25 2015
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