a(1)=2. For n >=2, a(n) = the least integer >= a(n-1) that is not coprime to both a(n-1)+1 and a(n-1).

A140525

a(1)=2. For n >=2, a(n) = the least integer >= a(n-1) that is not coprime to both a(n-1)+1 and a(n-1).

Terms

    a(0) =2a(1) =6a(2) =14a(3) =18a(4) =38a(5) =42a(6) =86a(7) =90a(8) =98a(9) =102a(10) =206a(11) =210a(12) =422a(13) =426a(14) =434a(15) =438a(16) =878a(17) =882a(18) =1766a(19) =1770a(20) =1778a(21) =1782a(22) =3566a(23) =3570a(24) =7142a(25) =7146a(26) =7154a(27) =7158a(28) =14318a(29) =14322

External references