login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

For all n, the set including the terms {a(1), a(2), a(3), ..., a(n)} has a nonprime number of digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.
1

%I #13 Mar 23 2017 14:36:10

%S 1,2,3,4,5,6,7,8,9,111,11,101,222,22,122,12,112,333,33,444,44,555,55,

%T 666,66,777,77,888,88,999,99,1111,1122,1133,13,31,1144,14,41,133,144,

%U 1155,115,15,155,166,16,116,177,17,117,1166,188,18,118,199,19,91,212,121,21,221,313,223,23,233,331,113,131,414,114,224

%N For all n, the set including the terms {a(1), a(2), a(3), ..., a(n)} has a nonprime number of digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

%C The sequence is started with a(1) = 1 and always extended with the smallest integer not yet present and not leading to a contradiction.

%H Jean-Marc Falcoz, <a href="/A283868/b283868.txt">Table of n, a(n) for n = 1..3000</a>

%e The set consisting of the first 15 terms is {1,2,3,4,5,6,7,8,9,111,11,101,222,22,122}; we count one 0, nine 1's, eight 2's, one 3, one 4, one 5, etc. All those quantities of digits are nonprime numbers.

%K nonn,base

%O 1,2

%A _Eric Angelini_ and _Jean-Marc Falcoz_, Mar 17 2017