%I A007921
%S A007921 7,13,19,23,25,31,33,37,43,47,49,53,55,61,63,67,73,75,79,83,85,
%T A007921 89,91,93,97,103,109,113,115,117,119,121,123,127,131,133,139,141,
%U A007921 143,145,151,153,157,159,163,167,169,173,175,181,183,185,187,193
%N A007921 Numbers that are not the difference of two primes.
%D A007921 F. Smarandache, Properties of Numbers, 1972. (See Smarandache odd sieve.)
%D A007921 F. Smarandache, "Only Problems, not Solutions!", Xiquan Publ., Phoenix-Chicago, 
               1993
%H A007921 T. D. Noe, <a href="b007921.txt">Table of n, a(n) for n=1..10000</a>
%H A007921 C. Dumitrescu & V. Seleacu, editors, <a href="http://www.gallup.unm.edu/
               ~smarandache/SNAQINT.txt">Some Notions and Questions in Number Theory, 
               Vol. I</a>.
%H A007921 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">
               Only Problems, Not Solutions!</a>
%H A007921 <a href="Sindx_Pri.html#gaps">Index entries for primes, gaps between</
               a>
%F A007921 Odd numbers n such that n+2 is composite.
%Y A007921 Cf. A048859.
%Y A007921 Complement of A030173. Cf. A001223.
%Y A007921 Equals A005381(2n-1) - 1.
%Y A007921 Sequence in context: A074628 A031194 A121058 this_sequence A092409 A124095 
               A109369
%Y A007921 Adjacent sequences: A007918 A007919 A007920 this_sequence A007922 A007923 
               A007924
%K A007921 nonn,easy,nice
%O A007921 1,1
%A A007921 R. Muller