2,1

Are there any further terms?

(PARI) twopm1(n) = { sr=0; forprime(x=2, n, y=2^x-1; if(isprime(x+2), y2=2^(x+2)-1, y2=0); if(isprime(y) && isprime(x+2), print1(x", "); sr+=1.0/y; sr+=1.0/y2; ) ); }

Sequence in context: A102846 A100003 A114161 this_sequence A084723 A107312 A083213

Adjacent sequences: A087855 A087856 A087857 this_sequence A087859 A087860 A087861

easy,nonn

Cino Hilliard (hillcino368(AT)gmail.com), Oct 25 2003