a(0)=a(1)=1; for n>1, a(n) = 2*a(n-1) + 1 if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1),n).

A133580

a(0)=a(1)=1; for n>1, a(n) = 2*a(n-1) + 1 if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1),n).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =1a(4) =3a(5) =7a(6) =15a(7) =31a(8) =63a(9) =7a(10) =15a(11) =31a(12) =63a(13) =127a(14) =255a(15) =17a(16) =35a(17) =71a(18) =143a(19) =287a(20) =575a(21) =1151a(22) =2303a(23) =4607a(24) =9215a(25) =1843a(26) =3687a(27) =1229a(28) =2459a(29) =4919

External references