%I A122257
%S A122257 0,1,1,0,1,0,1,0,0,0,0,0,1,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T A122257 0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A122257 0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0
%N A122257 Characteristic function of Pierpont primes.
%C A122257 a(n) = if (n is prime) and (n-1 is 3-smooth) then 1 else 0.
%C A122257 a(n) = if n=1 then 0 else A122258(n) - A122258(n-1);
%C A122257 a(A122259(n)) = 0, a(A005109(n)) = 1.
%H A122257 <a href="Sindx_Ch.html#char_fns">Index entries for characteristic functions</
               a>
%H A122257 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               PierpontPrime.html">Pierpont Prime</a>
%F A122257 a(n) = A010051(n) * A065333(n-1).
%Y A122257 Sequence in context: A143222 A010060 A118247 this_sequence A129950 A010051 
               A131929
%Y A122257 Adjacent sequences: A122254 A122255 A122256 this_sequence A122258 A122259 
               A122260
%K A122257 nonn
%O A122257 1,1
%A A122257 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 29 2006