%I A090465
%S A090465 1,0,0,2,0,1,0,1,1,1,0,1,0,1,1,2,0,1,0,2,1,1,0,1,3,1,1,4,0,1,0,2,1,1,1,
               1,0,
%T A090465 1,1,1,0,1,0,1,1,16,0,1,1,1,1,3,0,1,5,1,1,15,0,1,0,2,1,12,1,1,0,2,1,1,
               0,1,
%U A090465 0,2,1,1,3,1,0,1,1,1,0,1,1,2,1,33,0,1,1,1,1,3,10,1,0,3,1,1,0,1,0,1,1,1,
               0,1
%V A090465 1,0,0,2,0,-1,0,1,-1,1,0,-1,0,1,-1,2,0,-1,0,2,-1,1,0,-1,3,1,-1,4,0,-1,
               0,2,-1,1,1,-1,0,
%W A090465 1,-1,1,0,-1,0,1,-1,16,0,-1,1,1,-1,3,0,-1,5,1,-1,15,0,-1,0,2,-1,12,1,-1,
               0,2,-1,1,0,-1,
%X A090465 0,2,-1,1,3,-1,0,1,-1,1,0,-1,1,2,-1,33,0,-1,1,1,-1,3,10,-1,0,3,-1,1,0,
               -1,0,1,-1,1,0,-1
%N A090465 Smallest number m such that n followed by m nines yields a prime or -1 
               if no solution exists or has been found for n.
%C A090465 a(n) = 0 if n is already prime. a(n) = -1 for n = any multiple of 3 other 
               than 3 itself. The first 9 record holders in this sequence are 1, 
               4, 25, 28, 46, 88, 374, 416, 466 with the values 1, 2, 3, 4, 16, 
               33, 57, 70, 203 respectively.
%e A090465 a(25)=3 because three 9's must be appended to 25 before a prime is formed 
               (25999). a(6) = -1 because no matter how many 9's are appended to 
               6, the resulting number is always divisible by 3 and can therefore 
               not be prime.
%Y A090465 Cf. A083747 (The Wilde Primes, i.e. same operation using ones), A090464 
               (using sevens), A090584 (using threes).
%Y A090465 Sequence in context: A082886 A097304 A136745 this_sequence A052344 A147768 
               A167746
%Y A090465 Adjacent sequences: A090462 A090463 A090464 this_sequence A090466 A090467 
               A090468
%K A090465 base,sign
%O A090465 1,4
%A A090465 Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 02 2003