%I A037273
%S A037273 0,0,0,2,0,1,0,13,2,4,0,1,0,5,4,4,0,1,0,15,1,1,0,2,3,4,4,1,0,2,0,2,1,5,
%T A037273 3,2,0,2,1,9,0,2,0,9,6,1,0,15
%N A037273 Number of steps to reach a prime under "replace n by concatenation of 
               its prime factors", or -1 if no such number.
%H A037273 P. De Geest, <a href="http://www.worldofnumbers.com/topic1.htm">Home 
               Primes</a>
%H A037273 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               HomePrime.html">Link to a section of The World of Mathematics.</a>
%e A037273 Starting with 14 we get 14=2*7, 27=3*3*3, 333=3*3*37, 3337=47*71, 4771=13*367, 
               13367 is prime; so a(14)=5.
%Y A037273 Cf. A037271-A037275, A056938.
%Y A037273 Sequence in context: A049218 A154469 A022902 this_sequence A158924 A025426 
               A053200
%Y A037273 Adjacent sequences: A037270 A037271 A037272 this_sequence A037274 A037275 
               A037276
%K A037273 nonn,nice,hard
%O A037273 1,4
%A A037273 N. J. A. Sloane (njas(AT)research.att.com), Jeff Burch (gburch(AT)erols.com)
%E A037273 Starting with 49, no prime has been reached after 79 steps.