%I A104172
%S A104172 0,0,2,3,3,0,5,5,0,0,0,0,0,0,0,0,0,11,11,0,0,0,0,0,0,0,0,0,0,0,0,17,17,
%T A104172 0,0,19,0,0,0,0,23,23,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,31,0,
%U A104172 0,0,0,0,37,0,0,0,0,0,0,0,41,43,0,43,43,0,0,0,47,47,0,0,0,0,0,0,0,0,41
%N A104172 Replace nonprimes in A005185 by zeros.
%F A104172 a(n) = if Hofstadter[n] is prime then Hofstadter[n] else zero
%t A104172 digits = 200 Hofstadter[n_Integer? Positive] := Hofstadter[n] = Hofstadter[n 
               - Hofstadter[n - 1]] + Hofstadter[n - Hofstadter[n - 2]] Hofstadter[0] 
               = Hofstadter[1] = 1 b = Table[If[PrimeQ[ Hofstadter[n]] == True, 
               Hofstadter[n], 0], {n, 0, digits - 1}]
%Y A104172 Cf. A005185.
%Y A104172 Sequence in context: A021815 A075255 A135498 this_sequence A091408 A106242 
               A121474
%Y A104172 Adjacent sequences: A104169 A104170 A104171 this_sequence A104173 A104174 
               A104175
%K A104172 nonn
%O A104172 0,3
%A A104172 Roger Bagula (rlbagulatftn(AT)yahoo.com), Mar 10 2005