A084599 a(1) = 2, a(2) = 3; for n >= 2, a(n+1) is largest prime factor of (Product_{k=1..n} a(k)) - 1.
2, 3, 5, 29, 79, 68729, 3739, 6221191, 157170297801581, 70724343608203457341903, 46316297682014731387158877659877, 78592684042614093322289223662773, 181891012640244955605725966274974474087, 547275580337664165337990140111772164867508038795347198579326533639132704344301831464707648235639448747816483406685904347568344407941
Offset: 1
Keywords
Examples
a(4)=29 since 2*3*5=30 and 29 is the largest prime factor of 30-1 a(5)=79 since 2*3*5*29=870 and 79 is the largest prime factor of 870-1=869=11*79.
Links
- Dario Alpern, Factorization using the Elliptic Curve Method
Extensions
More terms from Hugo Pfoertner, May 31 2003, using Dario Alpern's ECM.
The next term a(15) is not known. It requires the factorization of the 245-digit composite number which remains after eliminating 7 smaller factors.
Comments