%I #10 Mar 11 2014 01:32:50
%S 2,7,17,43,53,79,89,139,149,199,227,263,313,347,373,383,409,419,541,
%T 557,593,619,641,677,727,743,769,797,823,839,983,1009,1019,1069,1091,
%U 1117,1151,1187,1213,1223,1249,1259,1381,1409,1459,1481,1531,1553,1579,1601
%N a(1)=2. a(n) = the smallest prime p > a(n-1) such that p-a(n-1)-1 is composite.
%C A175121(n) = A175120(n+1) - A175120(n) - 1.
%H Harvey P. Dale, <a href="/A175120/b175120.txt">Table of n, a(n) for n = 1..1000</a>
%t sp[n_]:=Module[{np=NextPrime[n],pa1},pa1=np-n-1;While[PrimeQ[pa1] || pa1==1,np=NextPrime[np];pa1=np-n-1];np]; Join[{2},NestList[sp,7,50]] (* _Harvey P. Dale_, Jan 10 2012 *)
%Y A175118, A175121
%K nonn
%O 1,1
%A _Leroy Quet_, Feb 14 2010
%E Extended by _R. J. Mathar_, Feb 21 2010