%I #2 Mar 30 2012 17:33:53

%S 3,7,31,127,8191,131071,524287,2147483647,137438953471,2199023255551,

%T 8796093022207,9007199254740991,2305843009213693951,

%U 147573952589676412927,9444732965739290427391

%N Numbers of the form 2^p - 1, where p is a prime number that is not the sum, minus 1, of a Pythagorean triple.

%C See A136003 for the values of p.

%F a(n) = 2^A136003(n) - 1.

%e a(3)=31 because A136003(3)=5 and 2^5=32 and 32-1=31.

%Y Cf. A000079, A000668, A136002, A136003.

%K nonn

%O 1,1

%A _Omar E. Pol_, Dec 17 2007