%I A091089
%S A091089 16557,16718,26378,35921,46524,46867,50018,55187,58374,58452,60850,
%T A091089 63714,68771,71299,78035,78269,81661,84213,89052,90157,95490,97080,
%U A091089 102892,105690,108682,115558,115994,116138,116305,121097,128192,131194
%N A091089 Numbers which form a prime by appending a 3-digit odd number and form 
               no primes by appending any 1- or 2-digit odd number.
%C A091089 Many numbers become prime by appending a one-digit odd number. Some numbers 
               (such as 20, 32, 51, etc.) require a 2-digit odd number (A032352 
               has these). In the first 100,000 values of n there are only 22 that 
               require a 3-digit odd number. There probably are some values that 
               require odd numbers of 4 or more digits, but these are likely to 
               be very large.
%e A091089 a(1)=16557 because 16557 is first number which which requires a 3-digit 
               odd number be appended to it to form a prime. 165571, 165573, 165575, 
               ..., 165579, 1655711, 1655713, ..., 1655799 are all nonprime numbers. 
               16557103 is the first prime formed by appending odd numbers to 16657. 
               a(2) = 16718 because 16718111 is the first prime formed by appending 
               odd numbers to 16718.
%Y A091089 Cf. A032352 (a(n) requires at least a 2-digit odd number), A068695 (minimum 
               odd number that must be appended to n to form a prime).
%Y A091089 Sequence in context: A031829 A057680 A157796 this_sequence A109028 A057329 
               A108843
%Y A091089 Adjacent sequences: A091086 A091087 A091088 this_sequence A091090 A091091 
               A091092
%K A091089 base,nonn
%O A091089 1,1
%A A091089 Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 18 2003